Hi, Somehow, it doesn't work in my allegro, using SLIME PQ> (defun fact (n) (if (= n 1) 1 (* n (fact (1- n))))) FACT PQ> (fact 3) 6 PQ> (compile 'fact) FACT NIL NIL PQ> :step nil NIL PQ> (step fact) (FACT) PQ> (fact 3) 6 PQ> I'd appreciate any suggestions. Roman