Non-motor symptoms (NMS) of Parkinson's disease (PD) are a key determinant of health, quality of life (QoL) and societal cost of PD. They are often less appreciated than motor symptoms but are important sources of disability for manyPDpatients. Literature search was performed using the reference databases Medline, Science Citation Index and EMBASE. The keywords used were 'non-motor symptoms', Parkinson's disease, olfaction and constipation. Papers discovered by this search were reviewed, as were references cited therein.