Rats were treated with either (-)- or (+)-deprenyl, and the metabolites extracted from the plasma, liver, kidney and heart homogenates were studied by chiral capillary electrophoresis (CE). Stereoselective dealkylation of both optical isomers with the formation of desmethyldeprenyl (DD), methamphetamine (MA), and amphetamine (A) was found. (-)-MA appears to be the main metabolite of (-)-D, and (+)-A for (+)-D. This suggests that the enantiomers undergo a different dealkylation process.