Robert, This is a very complex evaluation to do, since most of the published benchmarks will give you different results for the same rules engine. :) Also, the first and third links you listed bellow, all refer to Drools 2.xseries that were not Rete complete implementations. Just to show you the difference between drools 2.x and 3.x, check this: http://blog.athico.com/2006/11/rush-hour-and-content-based-routing.html Drools 4.x is even faster for complex rules scenarios with lots of partial matches. The testimonies though are good for you to check out as they are recent testimonies. Best thing to do would be, if possible, to build a prototype with a use case closer to what you need and check the numbers out. We are sure that on a face to face performance comparison, you will be pleasant surprised with the power of the Drools rules engine. If you need help on the prototype, just mail the list, or if you want official support for it, just contact Red Hat. Regards, Edson 2007/8/1, Robert Mertens <rmertens(a)bobm.org&gt;: -- Edson Tirelli Software Engineer - JBoss Rules Core Developer Office: +55 11 3529-6000 Mobile: +55 11 9287-5646 JBoss, a division of Red Hat @ www.jboss.com