I have a single rule in my test bed as such: rule "5th Item Not Test" when $first : FirstClass($i1 : item1, $i2 : item2, $i3 : item3, $i4 : item4, $i5 : item5) not SecondClass(item1 == $i1, item2 == $i2, item3 == $i3, item4 == $i4, item5 == $i5) then System.out.println("NOT test matched"); end In the not SecondClass() section of the test, the last equality checks always fail, no matter what it is. I can switch the order around of the checks, no matter what the last 2 are, they cause THEN clause to not fire, even when I am absolutely positive there is not a match. (I can remove the not and the equality works fine). Is there a limit on the number of equality tests I can do with a not? It seems as though it is 4. I have attached a test case that can reproduce this (it is different from my project's code, but I have been able to reproduce this in multiple projects). It is a maven Eclipse project and includes a junit with some minor instructions. If these instructions do not make sense, please email me.