The diagnosis of Parkinson's disease (PD) is difficult despite the use of strict clinical criteria. Apomorphine (APP) is a strong dopaminergic D1 and D2 agonist which has been used as a diagnostic test for PD by several authors. Sixty patients with a Parkinson's syndrome received subcutaneous doses of APP with diagnostic objectives. Ninety-four percent of the subjects with clinical criteria of PD responded positively to the bolus of subcutaneous APP. The remaining six percent had secondary effects limiting the usefulness of the test. Two point seven percent of the patients with atypical data of PD improved during performance of the test. Despite the limitations, this easily carried out test may be added to the recently proposed criteria of clinical diagnosis and may contribute greater certainty in diagnosis.