Using the latest SVN revision: When using the "stat.child.0" syntax to add Statistics instances to steady-state evolution, the method SteadyStateEvolutionState.checkStatistics(), which is called from setup(), assumes that the "base" Parameter passed in will have the value P_STATISTICS. In fact, the base Parameter used by SteadyStateEvolutionState.setup() is null, so we get a NPE during initialization. A simple fix is to replace "base" with "new Parameter(P_STATISTICS)" in the call to checkStatistics on line 101. Cheers, Siggy -- Ph.D student in Computer Science George Mason University http://mason.gmu.edu/~escott8/