The objective of this paper is to evaluate the health-related quality of life in a community-based population of patients with Parkinson's disease (PD). The PD population consisted of 233 patients and was derived from a wider prevalence study in the county of Rogaland, Norway. The quality of life was measured by the Nottingham Health Profile (NHP) and four general health and well-being questions. The results were compared with quality of life measurements in 100 patients with diabetes mellitus (DM) and 100 healthy elderly people. The control groups had the same age and sex distribution as the patients with PD. This study showed that PD has a substantial impact on the health-related quality of life. Patients with PD had higher distress scores in all measured dimensions of the NHP than the two control groups. The negative impact of PD was highest for physical mobility, emotional reactions, social isolation and energy. Correlation analysis of the quality of life showed that age, duration of levodopa therapy, higher levodopa doses, depression, cognitive impairment and more advanced disease correlated with higher distress scores in patients with PD. The results of this study showed that PD had a broad impact on well-being, more so than DM. The distress related to the severity of the disease, as well as to depressive symptoms and cognitive impairment. An important finding was the underestimated distress related to lack of energy. Copyright 1998 Lippincott Williams & Wilkins