Smullyan's notion of eeectively inseparable pairs of sets is not the best eeec-tive/constructive analog of Kleene's notion of pairs of sets inseparable by a recursive set. We present a corrected notion of eeectively inseparable pairs of sets, prove a characterization of our notion, and show that the pairs of index sets eeectively inseparable in Smullyan's sense are the same as those eeectively ...