Khat leaves, widely used as a stimulant in East Africa and the Arab Peninsula, contain the alkaloid (-)-cathinone. The effects of this substance on the efflux of radioactivity from rabbit striatal slices prelabelled with 3H-dopamine were examined. It was found that low concentrations of (-)cathinone enhance the release of radioactivity in a dose-dependent manner, and that (-)cathinone was capable of sustaining the enhanced release induced by (+)amphetamine. Pretreatment of the tissue with cocaine, which is known to prevent the induction of release by (+)amphetamine, inhibited the efflux increase caused by (-)-cathinone. These observations suggest that amphetamine and the active principle of khat leaves have an analogous mechanism of action.