A few versions ago, I think the following simplified to zero; now it doesn't: (%i6) sqrt(3) * sqrt(17) - sqrt(51); (%o6) sqrt(3) sqrt(17) - sqrt(51) Both CVS Maxima and 5.15.0 will not simplify %i6 to zero. If this is a new bug, it's sad that the test suite didn't catch it. Barton