Noreximide, a sedative, is generally contaminated to some extent with its endo-isomer, norendimide, which produces excitation. Noreximide is an investigational drug which displays a peculiar activity on the central nervous system in laboratory animals and in humans. The compound was selected as the most promising member from a series of analogous dicarboxylic acid imides, after a Hansch correlation analysis of the biological activities to some physicochemical properties. The preceding pharmacological and toxicological screening yielded satisfactory results and the compound was undergoing extensive clinical trials in psychiatric patients.