These notes are intended to provide guidance for the evaluation of drugs in the treatment of Parkinson's disease. They should be read in conjunction with the Directive 75/318/EEC and 83-570/EEC and current and future EC and ICH guidelines, especially those on: Studies in support of special populations: geriatrics (ICH E7). The extent of population exposure to assess clinical safety for drugs intended for long-term treatment in non life threatening conditions (ICH E1). General considerations for clinical trials (ICH-E8). Statistical principles for clinical trials (ICH-E9). Pharmacokinetic studies in man Clinical testing of prolonged action forms, with special reference to extended release forms. Dose response information to support product authorisation