The purpose of the present investigation was to examine the effect of N-monomethylation of phenylisopropylamine derivatives on amphetamine-like activity. In tests of stimulus generalization using rats trained to discriminate 1.0 mg/kg of (+)-amphetamine from saline, the N-monomethyl derivatives of 1-(X-phenyl)-2-aminopropane, where X = 2,4-dimethoxy (2,4-DMA), 3,4-dimethoxy (3,4-DMA), 2,4,5-trimethoxy (2,4,5,-TMA), and 2-methoxy-4,5-methylenedioxy (MMDA-2), did not produce amphetamine-appropriate responding at the doses evaluated. However, the N-monomethyl derivative of cathinone (i.e., methcathinone), like cathinone, resulted in stimulus generalization. Further studies with this agent revealed that (a) in the amphetamine-trained animals, methcathinone (ED50 = 0.37 mg/kg) is more potent than racemic cathinone or racemic amphetamine (ED50 = 0.71 mg/kg in both cases), (b) methcathinone is capable of inducing release of radioactivity from [3H]dopamine-prelabeled tissue of rat caudate nucleus in a manner similar to that observed with cathinone, amphetamine, and methamphetamine, and (c) methcathinone is more potent than cathinone as a locomotor stimulant in mice as determined by their effect on spontaneous activity. The results of the present study provide evidence for a structural analogy between the prototypic psychostimulants amphetamine/methamphetamine and cathinone/methcathinone, and lend further support to the concept that amphetamine and cathinone correspond in their pharmacological effects.