Testosterone pretreatment (1.0-4.0 mg/kg) attenuated, in a dose-response fashion, the induction of stereotyped behavior and hyperactivity by pargyline (0.25, 4.0 mg/kg) and beta-phenylethylamine (8.0, 16.0 mg/kg) in preubertal, male rats. The dyskinetic movements induced by pargyline and beta-phenylethylamine were proposed as a possible animal model for tardive dyskinesias. Attenuation by testosterone of these effects suggested an hormonal involvement consistent with the reported predominant occurrence of tardive dyskinesias in women and in the elderly.