See http://code.google.com/p/plop/wiki/QuickStart for an installation guide a brief tour. A note on random numbers: based on some rather unscientific and limited tests, it appears that the clisp prng is not very good. For example, consider: (defun zzz () (do ((l (loop for n from 1 to 500 collect (< (let ((x 0)) (dotimes (i 99999) (if (eql (random 2) 0) (incf x))) x) 50000)) (cddr l)) (a 0) (b 0) (c 0) (d 0)) ((not l) (list a b c d)) (if (car l) (if (cadr l) (incf a) (incf b)) (if (cadr l) (incf c) (incf d))))) Calling (zzz) repeatedly should produce lists of four elements all having the same expectation. This works find in sbcl, but in clisp (v2.43 on OSX) there is a consistent skew, e.g. (38 84 86 42), (37 86 89 38), (33 97 91 29), etc. I considered using the platform-independent http://www.cliki.net/MT19937 implementation, but found it to be 5-30 times slower - enough to matter in some use-cases. So proceed with caution, and use sbcl if you are running important experiments and want good randomness (note however that evolutionary algorithms in general don't seem to care how good your randomness is).