Conversion from standard levodopa to Sinemet CR was performed in a series of 450 patients with Parkinson's disease. Of these, 299 experienced motor complications (group A) and 151 showed stable motor response (group B). There was significant improvement in various parameters of efficacy (Unified Parkinson's Disease Rating Scale, Hoehn-Yahr staging, Schwab-England scale) particularly in those related to functional aspects such as activities of daily living of the Unified Parkinson's Disease Rating Scale, sleep questionnaires and the Nottingham Health Profile. Adverse effects were usually mild or moderate, and only 10% of patients discontinued Sinemet CR due to side effects. Sinemet CR treatment was preferred by 81% of patients in group A and by 73.8% of patients in group B.