Chapter 1 gives an overview of the relevance of studying therapy adherence in Parkinson’s disease. Chapter 2 examines drug induced neurological syndromes and considers the validity of patients’ concerns about taking prescribed medications. Chapter 3 compares different methods of assessing therapy adherence. Chapter 4 studies factors associated with sub-optimal medicine usage in 54 patients. Chapter 5 reports a study of patient perceived involvement with management decisions and an assessment of satisfaction with the movement disorder service in 107 patients. Chapter 6 explores patients’ beliefs about antiparkinson medication in 129 patients. Chapter 7 examines the effect on Parkinson’s patients of emerging data about drug side effects, specifically fibrosis due to ergot-based dopamine agonists. Chapter 8 reports on an educational intervention designed to improve Parkinson drug timing compliance. In summary, this thesis provides important new information about medicine taking in Parkinson’s disease. A fifth of PD patients take less than 80% of prescribed antiparkinson medication. Electronic monitoring is the only reliable method of accurately detecting sub-optimal medication usage. Patients who take less than 80% of prescribed medicines are more likely to be younger, have concomitant depression, be prescribed more tablets per day and have poorer quality of life. Patients are more satisfied if they are involved in management decisions and have increased intention to comply with prescribed medication if there is better communication. Poorer quality of life is associated with less intention to comply with prescribed medication. Timing of medication intake is generally irregular but can be improved by informing patients of the continuous dopaminergic theory and providing specific drug timings. Once daily drugs are taken more consistently than drugs with more frequent doses.