Sebum secretion was studied in 14 parkinsonian patients before and after 3 months of treatment with L-dopa. An abnormality of sebum secretion was shown to exist in parkinsonism. In 7 patients, successfully treated with L-dopa, sebum secretion diminished and its pattern improved. In all patients, in whom L-dopa treatment did not result in noticeable clinical changes, there was no significant modification in sebum secretion. No change was observed in the secretion of sebum of 5 normal control subjects, who were given L-dopa for 1 week.