Hi, Actually, I'm not sure about where the error comes from, so, I'll tell for two possibilities: 1)Eclipse itself is making a OutOfMemoryError 2)when you run you application using rules, you have a outOfMemoryError 1)Eclipse itself is maling a OutOfMemoryError -go in your eclipse installation folder -open the file name eclipse.ini -replace -Xmx512m by -Xmx1024m or whatever size should be appropriate 2) your application is doing it -right click on a source file -Run as -Run configurations... -Arguments -in vm arguments, just put -Xmx1024m or whatever size should be appropriate -- View this message in context: http://drools-java-rules-engine.46999.n3.nabble.com/Drools-5-0-1-in-eclip... Sent from the Drools - User mailing list archive at Nabble.com.