There would be an issue that subst(x,3,3+4*%i) would have to change #c(3 4) to ((mplus) $x #c(0 4)) and gobs of other related issues. One simpler way to "fix" this is to recognize complex numbers in the simplifier and change them to Maxima's representation. Just as the common lisp rational 3/4 could be (is it?) changed to ((rat) 3 4). RJF