The French Selegiline Multicenter Trial was carried out in 1990 to investigate whether the disability of de novo patients with parkinsonism could be improved during the first 3 months by monotherapy with selegiline (10mg/day). A double-blind, randomized, placebo-controlled clinical trial was conducted over 3 months with 93 patients from 13 centers. Symptomatology was assessed on various disease rating scales, including Hoehn and Yahr, Hamilton Depression Rating Scale, Unified Parkinson's Disease rating scale, and Schwab and England scores, as well as self-assessment. Biological and clinical parameters were measured for tolerability, and efficacy was investigated with special reference to the point at which therapy with L-dopa had to be started. Selegiline was significantly superior to placebo on the various motor rating scores, and depressive scores were significantly improved at the end of 3 months. Adverse effects were rare and minor. Therefore, selegiline could be the therapy of choice for the treatment of de novo parkinsonian patients.