Preliminary studies have shown that riluzole, a Na+ channel blocker with antiglutamatergic activity, has neuroprotective efficacy in several models of acute dopaminergic neurodegeneration. A chronic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) monkey model which comes closer to the slow evolution of Parkinson's disease has recently been developed in order to allow dynamic studies. The present results show that riluzole delayed the appearance of parkinsonian motor abnormalities in this dynamic model, using from 10.2 +/- 1.6 daily injections for the MPTP-treated monkeys (n = 4) to 16.5 +/- 2.0 daily injections for the MPTP + riluzole-treated monkeys (n = 4). These results strongly suggest that riluzole may be beneficial to slow down the rate of progression of Parkinson's disease.