diff --git a/src/EditSession.java b/src/EditSession.java
index 865c3567f..ff7fcc649 100644
--- a/src/EditSession.java
+++ b/src/EditSession.java
@@ -21,6 +21,7 @@ import com.sk89q.worldedit.*;
 import com.sk89q.worldedit.regions.*;
 import com.sk89q.worldedit.blocks.*;
 import com.sk89q.worldedit.data.*;
+import com.sk89q.worldedit.patterns.*;
 import java.io.IOException;
 import java.util.Map;
 import java.util.HashMap;
@@ -515,9 +516,16 @@ public class EditSession {
             Vector min = region.getMinimumPoint();
             Vector max = region.getMaximumPoint();
 
-            for (int x = min.getBlockX(); x <= max.getBlockX(); x++) {
-                for (int y = min.getBlockY(); y <= max.getBlockY(); y++) {
-                    for (int z = min.getBlockZ(); z <= max.getBlockZ(); z++) {
+            int minX = min.getBlockX();
+            int minY = min.getBlockY();
+            int minZ = min.getBlockZ();
+            int maxX = max.getBlockX();
+            int maxY = max.getBlockY();
+            int maxZ = max.getBlockZ();
+
+            for (int x = minX; x <= maxX; x++) {
+                for (int y = minY; y <= maxY; y++) {
+                    for (int z = minZ; z <= maxZ; z++) {
                         Vector pt = new Vector(x, y, z);
 
                         if (setBlock(pt, block)) {
@@ -537,6 +545,45 @@ public class EditSession {
         return affected;
     }
 
+    /**
+     * Sets all the blocks inside a region to a certain block type.
+     *
+     * @param region
+     * @param block
+     * @return number of blocks affected
+     * @throws MaxChangedBlocksException
+     */
+    public int setBlocks(Region region, Pattern pattern)
+            throws MaxChangedBlocksException {
+        int affected = 0;
+
+        if (region instanceof CuboidRegion) {
+            // Doing this for speed
+            Vector min = region.getMinimumPoint();
+            Vector max = region.getMaximumPoint();
+
+            for (int x = min.getBlockX(); x <= max.getBlockX(); x++) {
+                for (int y = min.getBlockY(); y <= max.getBlockY(); y++) {
+                    for (int z = min.getBlockZ(); z <= max.getBlockZ(); z++) {
+                        Vector pt = new Vector(x, y, z);
+
+                        if (setBlock(pt, pattern.next(pt))) {
+                            affected++;
+                        }
+                    }
+                }
+            }
+        } else {
+            for (Vector pt : region) {
+                if (setBlock(pt, pattern.next(pt))) {
+                    affected++;
+                }
+            }
+        }
+
+        return affected;
+    }
+
     /**
      * Replaces all the blocks of a type inside a region to another block type.
      *
diff --git a/src/WorldEditListener.java b/src/WorldEditListener.java
index 6c4e0c323..28cefa0ce 100644
--- a/src/WorldEditListener.java
+++ b/src/WorldEditListener.java
@@ -17,6 +17,8 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
 
+import java.util.List;
+import java.util.ArrayList;
 import java.util.Map;
 import java.util.HashMap;
 import java.util.Set;
@@ -31,6 +33,7 @@ import com.sk89q.worldedit.blocks.*;
 import com.sk89q.worldedit.data.*;
 import com.sk89q.worldedit.snapshots.*;
 import com.sk89q.worldedit.regions.*;
+import com.sk89q.worldedit.patterns.*;
 
 /**
  * Plugin base.
@@ -267,8 +270,47 @@ public class WorldEditListener extends PluginListener {
         return getBlock(id, false);
     }
 
+    /**
+     * Get a list of blocks as a set. This returns a Pattern.
+     *
+     * @param list
+     * @return pattern
+     */
+    public Pattern getBlockPattern(String list)
+            throws UnknownItemException, DisallowedItemException {
+
+        String[] items = list.split(",");
+
+        if (items.length == 1) {
+            return new SingleBlockPattern(getBlock(items[0]));
+        }
+
+        List<BlockChance> blockChances = new ArrayList<BlockChance>();
+
+        for (String s : items) {
+            BaseBlock block;
+            
+            double chance;
+            if (s.matches("[0-9]+(?:\\.(?:[0-9]+)?)?%.*")) {
+                String[] p = s.split("%");
+                chance = Double.parseDouble(p[0]);
+                block = getBlock(p[1]);
+            } else {
+                chance = 1;
+                block = getBlock(s);
+            }
+            
+            blockChances.add(new BlockChance(block, chance));
+        }
+
+        return new RandomFillPattern(blockChances);
+    }
+
     /**
      * Get a list of blocks as a set.
+     *
+     * @param list
+     * @return set
      */
     public Set<Integer> getBlockIDs(String list) throws UnknownItemException,
                                                       DisallowedItemException {
@@ -723,8 +765,14 @@ public class WorldEditListener extends PluginListener {
         // Replace all blocks in the region
         } else if(split[0].equalsIgnoreCase("//set")) {
             checkArgs(split, 1, 1, split[0]);
-            BaseBlock block = getBlock(split[1]);
-            int affected = editSession.setBlocks(session.getRegion(), block);
+            Pattern pattern = getBlockPattern(split[1]);
+            int affected;
+            if (pattern instanceof SingleBlockPattern) {
+                affected = editSession.setBlocks(session.getRegion(),
+                        ((SingleBlockPattern)pattern).getBlock());
+            } else {
+                affected = editSession.setBlocks(session.getRegion(), pattern);
+            }
             player.print(affected + " block(s) have been changed.");
 
             return true;
diff --git a/src/com/sk89q/worldedit/patterns/BlockChance.java b/src/com/sk89q/worldedit/patterns/BlockChance.java
new file mode 100644
index 000000000..e28e80e97
--- /dev/null
+++ b/src/com/sk89q/worldedit/patterns/BlockChance.java
@@ -0,0 +1,63 @@
+// $Id$
+/*
+ * WorldEdit
+ * Copyright (C) 2010 sk89q <http://www.sk89q.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package com.sk89q.worldedit.patterns;
+
+import com.sk89q.worldedit.blocks.BaseBlock;
+
+/**
+ * Gives a block a chance.
+ *
+ * @author sk89q
+ */
+public class BlockChance {
+    /**
+     * Block.
+     */
+    private BaseBlock block;
+    /**
+     * Chance. Can be any positive value.
+     */
+    private double chance;
+
+    /**
+     * Construct the object.
+     * 
+     * @param block
+     * @param chance
+     */
+    public BlockChance(BaseBlock block, double chance) {
+        this.block = block;
+        this.chance = chance;
+    }
+
+    /**
+     * @return the block
+     */
+    public BaseBlock getBlock() {
+        return block;
+    }
+
+    /**
+     * @return the chance
+     */
+    public double getChance() {
+        return chance;
+    }
+}
diff --git a/src/com/sk89q/worldedit/patterns/Pattern.java b/src/com/sk89q/worldedit/patterns/Pattern.java
new file mode 100644
index 000000000..d5d84e4c6
--- /dev/null
+++ b/src/com/sk89q/worldedit/patterns/Pattern.java
@@ -0,0 +1,40 @@
+// $Id$
+/*
+ * WorldEdit
+ * Copyright (C) 2010 sk89q <http://www.sk89q.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package com.sk89q.worldedit.patterns;
+
+import com.sk89q.worldedit.*;
+import com.sk89q.worldedit.blocks.BaseBlock;
+
+/**
+ * Used to get the block to set. This can be used to implement a pattern
+ * for when setting a region with blocks.
+ *
+ * @author sk89q
+ */
+public interface Pattern {
+    /**
+     * Get a block for a position. This return value of this method does
+     * not have to be consistent for the same position.
+     *
+     * @param pos
+     * @return
+     */
+    public BaseBlock next(Vector pos);
+}
diff --git a/src/com/sk89q/worldedit/patterns/RandomFillPattern.java b/src/com/sk89q/worldedit/patterns/RandomFillPattern.java
new file mode 100644
index 000000000..765134e79
--- /dev/null
+++ b/src/com/sk89q/worldedit/patterns/RandomFillPattern.java
@@ -0,0 +1,85 @@
+// $Id$
+/*
+ * WorldEdit
+ * Copyright (C) 2010 sk89q <http://www.sk89q.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package com.sk89q.worldedit.patterns;
+
+import java.util.Random;
+import java.util.List;
+import java.util.ArrayList;
+import com.sk89q.worldedit.*;
+import com.sk89q.worldedit.blocks.BaseBlock;
+
+/**
+ * Pattern proportionally fills.
+ *
+ * @author sk89q
+ */
+public class RandomFillPattern implements Pattern {
+    /**
+     * Random number generator.
+     */
+    private static final Random random = new Random();
+    /**
+     * Blocks and their proportions.
+     */
+    private List<BlockChance> blocks;
+
+    /**
+     * Construct the object.
+     *
+     * @param blockType
+     */
+    public RandomFillPattern(List<BlockChance> blocks) {
+        double max = 0;
+
+        for (BlockChance block : blocks) {
+            max += block.getChance();
+        }
+
+        List<BlockChance> finalBlocks = new ArrayList<BlockChance>();
+
+        double i = 0;
+
+        for (BlockChance block : blocks) {
+            double v = block.getChance() / max;
+            i += v;
+            finalBlocks.add(new BlockChance(block.getBlock(), i));
+        }
+
+        this.blocks = finalBlocks;
+    }
+
+    /**
+     * Get next block.
+     *
+     * @param pos
+     * @return
+     */
+    public BaseBlock next(Vector pos) {
+        double r = random.nextDouble();
+        
+        for (BlockChance block : blocks) {
+            if (r <= block.getChance()) {
+                return block.getBlock();
+            }
+        }
+
+        throw new RuntimeException("ProportionalFillPattern");
+    }
+}
diff --git a/src/com/sk89q/worldedit/patterns/SingleBlockPattern.java b/src/com/sk89q/worldedit/patterns/SingleBlockPattern.java
new file mode 100644
index 000000000..8bc996574
--- /dev/null
+++ b/src/com/sk89q/worldedit/patterns/SingleBlockPattern.java
@@ -0,0 +1,63 @@
+// $Id$
+/*
+ * WorldEdit
+ * Copyright (C) 2010 sk89q <http://www.sk89q.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package com.sk89q.worldedit.patterns;
+
+import com.sk89q.worldedit.*;
+import com.sk89q.worldedit.blocks.BaseBlock;
+
+/**
+ * Always returns the same block type.
+ *
+ * @author sk89q
+ */
+public class SingleBlockPattern implements Pattern {
+    /**
+     * Block type.
+     */
+    private BaseBlock block;
+
+    /**
+     * Construct the object.
+     * 
+     * @param blockType
+     */
+    public SingleBlockPattern(BaseBlock block) {
+        this.block = block;
+    }
+
+    /**
+     * Get next block.
+     * 
+     * @param pos
+     * @return
+     */
+    public BaseBlock next(Vector pos) {
+        return block;
+    }
+
+    /**
+     * Get the block.
+     * 
+     * @return
+     */
+    public BaseBlock getBlock() {
+        return block;
+    }
+}