Dihydroxyphenylalanine (dopa), the metabolic precursor of dopamine, was administered to 10 parkinsonian patients in oral doses of 1-5 g. and intravenous doses of 0.2-0.5 g. Increases in dopamine excretion of 100- to 1000-fold following the dopa administration indicated that dopa was being absorbed and metabolized. Only two of the 10 patients showed any objective improvement on this treatment. Although dopa did not show sufficient beneficial results in this study to be considered a useful therapeutic agent, its slight activity is consistent with other evidence suggesting that some extrapyramidal cells are sensitive to dopamine.