Howie, as I recall (my manual is missing and I must recall), the (defun (foo bar) (x) (mumble-frotz x)) was disallowed, but that the first arg to defun COULD be an arbitrary SETFable form. I guess you have to write (defun (getprop foo bar) (x) (mumble-frotz x)) [apologies for bastard CommonLisp, but as I said, I don't have my manual handy].