This study tested selected elements of a questionnaire devised to detect risk factors for osteoporosis in a large case-control study of hip fracture. The questions were applied to two separate studies. The first utilised a hospital sample of postmenopausal women with established vertebral osteoporosis, and responses were compared to woman with primary osteoarthritis. In a second study, the questionnaire was applied to apparently healthy women participating in a study of bone density. Significant differences between patients with osteoporosis and osteoarthritis were observed in body mass index, the prevalence of appendicular fractures, the degree of immobilisation, the age of menarche, exposure to sunlight and indices of physical activity. Significant differences were found in bone mass in healthy women divided according to the age of menarche, parity and duration of lactation. These data identify previously established risk factors for osteoporosis and suggest that the MEDOS questionnaire will provide a powerful tool for the future assessment of risk factors in osteoporosis.