Hopefully this is something I am doing incorrectly, however, when running the 4.0.X versions of the Drools engine in a multithreaded environment the rule occasionally gets the wrong answer. I have attached a simple example based on the drools-examples-drl structure which runs the engine and compares the result to a strictly Java rule equivalent. I have verified that the sample code will produce the incorrect results with 4.0.1, 4.0.2 and 4.0.3 version of the codebase. Additionally, it doesn’t seem to matter if I use stateless (which we use in production) or stateful sessions. The only work around we have found is to fully synchronize around any use of the Drools RuleBase methods. This doesn’t do us much good on our multi-cored systems. Thanks for any help on the issue. Tate Moore No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.503 / Virus Database: 269.15.12/1098 - Release Date: 2007-10-29 9:28 AM