The effects of thalidomide, a sedative, anti-inflammatory and immunosuppressive agent were studied in the MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) murine model of Parkinson's disease. The striatal levels of dopamine (DA) and of its main metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were measured both in the MPTP control group (3 x 15 mg/kg intraperitoneally) and in the thalidomide groups (repeated treatments at 25 mg/kg or 50 mg/kg postoperatively). For mice treated with thalidomide, a dose-dependent protection was observed against the MPTP-induced decrease in DA. The decrease in HVA levels was totally antagonized by thalidomide at both doses. That thalidomide has activity in this model suggests that an inflammatory process may be involved in the induction of lesions by MPTP in DAergic neurons.