In a detailed community study the total prevalence of idiopathic Parkinson's disease in Aberdeen was 164.2/10(5) of the population. The age and sex specific prevalence rose to 2657.8/10(5) (2.7%) of men and 2071.0/10(5) (2.0%) of women aged over 84. The mean age at onset, irrespective of sex, was 65.3 years (SD 12.6) and varied little compared with similar studies over the past 25 years. Half of patients were independent but 78/225 (34.7%) were considerably disabled and 23/225 (10.2%) were confined to bed or a wheelchair. Disability increased with age and also with a low minimental state questionnaire score. The score was less than or equal to 7/10 (graded 0-10) in 93/252 (37%) of patients and less than 5/10 in 28/252 (11%). Parkinson's disease remains a common and disabling condition in the community.