Previous studies of patients with primary osteoarthrosis of the hip have suggested an increase in bone mass compared with control populations. Nodal primary generalised osteoarthrosis is known to have a strong familial tendency. To test the hypothesis that this tendency might also lead to increased bone mass, total body calcium has been measured by in-vivo neutron activation analysis and cortical area calculated from measurements of metacarpal indices in 15 female patients with primary generalised osteoarthrosis. The results have been compared with those from 12 healthy controls matched for age, menopausal status, and skeletal size. No significant differences were noted in the total body calcium or cortical area measurements between the 2 groups either before or after correction for skeletal size and menopausal status. No relationship was found between the grade of radiological osteoarthrosis in the hand and either bone mass parameter. Bone mass would not appear to be an important factor in the aetiopathogenesis of nodal primary generalised osteoarthrosis.