Therapeutic responses to Sinemet CR were studied in 37 patients with early Parkinson's disease previously treated with standard (Madopar) or controlled-release (Madopar HBS) levodopa/benserazide combinations. Patients were followed up for a 3-month period. The optimal therapeutic response of parkinsonian disability to Sinemet CR was equal to that obtained with Madopar or Madopar HBS. The optimal therapeutic dosage of Sinemet CR was equal to that of Madopar HBS but 12% higher than that of standard Madopar. However, with Sinemet CR treatment, the number of daily doses needed was significantly fewer than with both previous treatments. End-of-dose failure, which had developed in 4 patients, and peak-dose dyskinesias present in 6 patients during treatment with standard Madopar, improved significantly with Sinemet CR. Thus, Sinemet CR seems to be beneficial and useful in the treatment of early Parkinson's disease.