Hi, Class VariableContextEntry and ReturnValueContextEntry are instantiated when Package.addRule called. This class are linked from "Package rules". "Package => ... => VariableContextEntry But class have a reference to the InternalWorkingMemory ! "Package => ... => VariableContextEntry => Workingmemory" When this pseudo code is executed, at the end of the execution, WorkingMemory need to be garbage collected, but it isn't because she is referenced by ReturnValueContextEntry and/or VariableContextEntry, and this class keeps an reference to the WorkingMemory. I think this can be generate some error in multi thread and make an "smal" memory leak. It is right ? The membre workingMemory can't be removed from VariableContextEntry/ReturnValueContextEntry ? ____________________ pseudo code (source : ReteooMannersTest) : final Package ruleBase = new Package( "org.drools.examples.manners" ); ruleBase.addRule( getAssignFirstSeatRule() ); ... SatefulSession session = ruleBase.newStatefulSession(false); session.insert(new Count(1)); session.fireAllRules(); session.dispose(); session = null; System.gc(); After GC, workingMemory (session) need to be finally but she isn't because VariableContextEntry/ReturnValueContextEntry keep a reference at the workingMemory. Thanks for your response Yves