The relationship between disability and various musculoskeletal disorders was investigated in 7217 men and women representative of the Finnish population aged 30 years or more. They participated in the Mini-Finland Health Survey and were first screened by interview and questionnaire about limitations in daily activities. The outcome variables were reduced working capacity, an occasional need for assistance in daily activities, and a regular need for assistance in daily activities. In a two-phase medical examination, all cases fulfilling predetermined diagnostic criteria of musculoskeletal, cardiovascular, respiratory and mental disorders and diabetes were recorded independently. In multivariate logistic regression analyses, inflammatory arthritis was the strongest determinant of all forms of disability. Osteoarthritis, especially in the hip, was a strong determinant of both occasional and regular need for assistance, and chronic low back pain was a strong determinant of reduced working capacity and occasional need for assistance among those aged 30-64 years. Other musculoskeletal disorders also determined the prevalence disability, but these relationships were reduced by taking comorbidity into account. A low level of education and a low (less than 20 kg/m2) or very high (at least 35 kg/m2) body mass index represented independent determinants of all forms of disability, and a history of physically strenuous work an independent determinant of reduced working capacity, when disabling illness was adjusted for. The proportion of all forms of disability attributable to musculoskeletal disorders, in models including, age, sex, other disabling illness and significant non-medical determinants of disability, was close to 20%. The disorders with the highest community impact were chronic low back pain among those aged 30-64, osteoarthritis of the hips and knees and inflammatory arthritis.