Christie, Blair wrote: What version of Drools? You have 2 million rules? Just to be clear, was it working with 1.9 million rules? heh I'm intigued on what sort of app you are doing, could you do a write up? I'm sure people would love to know about people using a really large number of rules. The limitation you reaching is a limitation of the standard serialisation algorithm of the JDK, we would have to create a custom marshaller to improve this further, which we may do in the future. Unless someone from the community wants to do this? :) Mark