Treatment of Parkinson's disease with L‐dopa therapy leads to long‐term complications, including loss of drug efficacy and the onset of dyskinesia. Adenosine A2Areceptors in striatum are selectively localized to GABAergic output neurons of the striato‐pallidal pathway and may avoid such problems. The novel adenosine A2Areceptor antagonist KW‐6002 has been examined for antiparkinsonian activity in MPTP‐treated primates. Oral administration of KW‐6002 reversed motor disability in MPTP‐treated common marmosets in a dose‐dependent manner. However, KW‐6002 only modestly increased overall locomotor activity and did not cause abnormal movement, such as stereotypy. The ability of KW‐6002 to reverse motor disability was maintained on repeated daily administration for 21 days, and no tolerance was observed. KW‐6002 induced little or no dyskinesia in MPTP‐treated primates previously primed to exhibit dyskinesia by prior exposure to L‐dopa. These results suggest that selective adenosine A2Areceptor antagonists represent a new class of antiparkinsonian agents that improve disability without producing hyperactivity and without inducing dyskinesia.