Objectives-Disturbances of cognition and emotion are common in patients with Parkinson's disease. Most previous studies of psychopathology in Parkinson's disease have focused on a single psychiatric diagnosis or condition. The objective of this study was to describe the range of neuropsychiatric symptoms in a representative sample of patients with Parkinson's disease. Methods-The sample of 139 patients was drawn from an epidemiological study of Parkinson's disease in Rogaland county, Norway, and represented 93% of those who had survived during the 4 years since the initial assessment. The diagnosis of Parkinson's disease was based on published criteria. Neuropsychiatric symptoms were assessed using the neuropsychiatric inventory, a caregiver based structured interview, which assesses severity and frequency of 10 psychiatric symptoms present during the past month. Results-At least one psychiatric symptom was reported in 61% of the sample. The most common behaviours were depression (38%) and hallucinations (27%), and the least common symptoms were euphoria and disinhibition. The highest mean scores were found for depression, apathy, and hallucinations. Factor analysis showed that hallucinations, delusions, and irritability clustered into one factor, and apathy and anxiety constituted another factor. Psychiatric symptoms were more common among patients living in nursing homes compared with home dwelling patients, and correlated with stage of disease and cognitive impairment, but not with age or duration of disease. No relation to left or right sided parkinsonism was found. Conclusion-This study emphasises the importance of psychiatric symptoms in Parkinson's disease, which were present in most patients. Clinicians should focus on the emotional and cognitive disturbances in addition to the motor manifestations of the disease. (J Neurol Neurosurg Psychiatry 1999;67:492-496)