Synthesis, X-ray, and cytotoxicity studies of (S)- and (R)-aziridine-2-carboxamide (Leakadine) are described. X-ray data for the enantiomericallypureform are compared with those for racemic aziridine-2-carboxamide in order to explain the 21°C large melting point difference between both series. It was found that despite their overall low cytotoxicity (S)-aziridine-2-carboxamide is slightly more cytotoxic