The optically pure isomers of cathinone were prepared by separating synthetic cathinone racemate and used to study central and peripheral effects of these indirect sympathomimetics in rats and guinea pigs. The (-)-isomer was significantly more potent than the (+)-isomer in stimulating locomotor activity whereas no difference was observed with respect to their cardiac effects. In analogy to observations with (+)- and (-)-amphetamine such variable isomer discrimination may be due to different stereoselectivities of amine uptake mechanisms in the target tissues.