The motor score with and without levodopa was estimated in 193 parkinsonian patients with variable length of evolution. The effect of levodopa on akinesia, rigidity, and tremor remained quite stable during the course of the disease. In contrast, the aggravation of gait disorder, postural instability, and dysarthria was more severe, with decreased percentage of improvement on levodopa in patients with longer evolution. It is suggested that aggravation of Parkinson's disease mainly results from increasing severity of cerebral nondopaminergic lesions.