The actions of dl-cathinone and d-amphetamine on operant responding were compared in rats. The effects of both drugs were predominantly suppressive on behaviour maintained by a Fixed Interval 2 minutes schedule of reward. Both drugs had equivalent durations of action in suppressing responding. The actions of the two compounds could be described as rate-dependent, although their rate-dependent actions could most parsimoniously be attributed to drug-induced rate constancy. Methysergide (10 mg/kg) had no significant differential effect on the response suppressant effects of the two compounds, even though in vitro studies have indicated that cathinone and amphetamine differ in their serotonin receptor affinity. The actions of cathinone were qualitatively similar to those of amphetamine in this behavioural test. Furthermore the observed potency ratio for dl-cathinone to d-amphetamine (1:3) was similar to that reported elsewhere in a range of other behavioural tests (anorexia, adipsia, drug-induced rotation, lethality) for this pair of isomers. The only major difference reported to date between the behavioural actions of cathinone and amphetamine relates to the unexpectedly weak potency of cathinone in the conditioned taste aversion procedure. Cathinone, the major active constituent of the Khat plant, is therefore a psychostimulant drug which may possess potent reinforcing properties by virtue of its amphetamine-like stimulant actions coupled with its very weak aversive properties.