The anti-tremor activity of talipexole (6-allyl-2-amino-5,6,7,8-tetrahydro-4 H-thiazolo[4,5- d]azepine dihydrochloride, B-HT 920 CL 2, Domin), a non-ergot dopamine D 2 receptor agonist which possesses α 2-adrenoceptor agonistic and 5-HT 3 receptor antagonistic properties, was examined in monkeys with a unilateral lesion in the ventromedial tegmentum. Talipexole dose dependently suppressed the tremor and had ED 50 values of 34 μg/kg s.c. and 84 μg/kg p.o. The anti-tremor effect of talipexole occurred at much lower doses than that of an ergot dopamine receptor agonist, bromocriptine (2-bromo-α-ergocryptine mesilate, ED 50; 2.5 mg/kg s.c.), and talipexole acted synergistically in combination with L-DOPA (3,4-dihydroxyphenylalanine). In ventromedial tegmentum-lesioned monkeys, anti-tremor doses of talipexole did not cause emetic behavior, but had sedative effects. Conversely, monkeys given bromocriptine exhibited oral movement, salivation and vomiting when anti-tremor effects were observed, but not marked sedative behavior at any of the doses investigated. During repeated administration of talipexole (a daily dose of 50 μg/kg s.c. for 21 days), the extent and duration of the anti-tremor effect did not change, but those of the sedative effect decreased gradually. The anti-tremor effect of talipexole was significantly suppressed by sulpiride, but not by SCH 23390 (7-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1 H-3-benzazepine-7-ol) or yohimbine, while the sedative effect was inhibited by sulpiride and yohimbine. The main metabolites of talipexole had no anti-tremor or sedative effects. These results indicate that talipexole exerts its anti-tremor activity via selective dopamine D 2 receptor stimulation.