diff --git a/prism/src/explicit/Distribution.java b/prism/src/explicit/Distribution.java
index fdda1de2..b54d5ecc 100644
--- a/prism/src/explicit/Distribution.java
+++ b/prism/src/explicit/Distribution.java
@@ -47,6 +47,19 @@ public class Distribution implements Iterable<Entry<Integer,Double>>
 		clear();
 	}
 	
+	/**
+	 * Copy constructor.
+	 */
+	public Distribution(Distribution distr)
+	{
+		this();
+		Iterator<Entry<Integer,Double>> i = distr.iterator();
+		while (i.hasNext()) {
+			Map.Entry<Integer,Double> e = i.next();
+			add(e.getKey(), e.getValue());
+		}
+	}
+	
 	/**
 	 * Clear all entries of the distribution.
 	 */
diff --git a/prism/src/explicit/MDP.java b/prism/src/explicit/MDP.java
index 18b3c6f6..6d5153fe 100644
--- a/prism/src/explicit/MDP.java
+++ b/prism/src/explicit/MDP.java
@@ -76,6 +76,21 @@ public class MDP extends Model
 		initialise(numStates);
 	}
 
+	/**
+	 * Constructor: new MDP copied from an existing DTMC.
+	 */
+	public MDP(DTMC dtmc)
+	{
+		this(dtmc.numStates);
+		for (int s : dtmc.getInitialStates()) {
+			addInitialState(s);
+		}
+		for (int s = 0; s < numStates; s++) {
+			addChoice(s, new Distribution(dtmc.getTransitions(s)));
+		}
+		// TODO: copy rewards, etc.
+	}
+
 	/**
 	 * Initialise: new model with fixed number of states.
 	 */