A case report describes a patient with AIDS (10-year evolution) and Parkinsonson's disease, treated with L-dopa (plus DOPA decarboxylase inhibitor [DCI]), 2400 mg indinavir per day, 500 mg zidovudine, and 300 mg lamivudine. Parkinsons had been diagnosed 5 years previously, treatment with L-dopa plus DCI was effective and well tolerated. After 1 month of treatment with the anti-HIV triple therapy and an unchanged daily dose of L-dopa, the patient developed severe dyskinesias occurring at the peak dose periods, whereas the on-periods lasted the whole day without fluctuations. The antiviral drugs were stopped and dyskinesias improved within 5 days. The antiviral drugs were later reintroduced separately for a minimum of 2 weeks. Indinavir alone induced the abnormal movements after 3 days of treatment but the two other antiviral drugs did not. Indinavir was definitively stopped and dyskinesias improved within 5 days, whereas the motor status worsened progressively with the reappearance of fluctuations. The authors suggest that as protease inhibitors inhibit the hepatic metabolism of several drugs by inhibition of cytochrome P450, which catalyzes oxidative reactions produced by MAO or COMT, the latency in appearance and disappearance of this adverse effect, namely, the enhanced effect of L-dopa, could be related to a progressive inhibition of proteases but also to delayed dopaminergic receptor hypersensitivity. When indinavir and catecholaminergic drugs have to be administered together, this should lead to a reduction in daily requirements of the latter.