Using high-pressure liquid chromatography with electrochemical detection, we measured dopamine (DA) and homovanillic acid (HVA) in caudate nucleus, putamen and substantia nigra in 4 untreated rhesus monkeys and 4 monkeys with permanent parkinsonism produced by repeated injections of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; total dose: 2.1-6.45 mg/kg, i.m.). MPTP consistently produced a severe striatal and nigral loss of DA and HVA and an increase in the ratio 'HVA/DA'. In this respect, MPTP mimicked the changes found in human Parkinson's disease (PD). However, MPTP lowered the DA in caudate (-99.6%) to the same degree as in putamen (-99.5%). This is in contrast to idiopathic PD where the caudate is significantly less affected by DA loss (-84%) than the putamen (-98%). Thus, in our rhesus monkeys MPTP failed to reproduce the interregional caudate-putamen gradient characteristic of idiopathic PD. The DA pattern produced by MPTP was similar to the DA loss in caudate (-98%) and putamen (-99%) observed in patients with postencephalitic parkinsonism.