[en] Two groups of investigators utilized three techniques for evaluating bone mineral mass. In one institution, total-body calcium by total body neutron activation analysis, and bone mineral content of the radius by photon absorptiometry were measured concomitantly. In the other institution, the mean bone mineral content of the three inner phalanges of the left hand was measured by radiographic absorptiometry. These techniques were applied to two groups of subjects: 16 patients with primary osteoporosis and 14 healthy marathon runners. The higher correlation found in osteoporotic patients may be related to the diffuse nature of this condition and to differences in the distribution of skeletal mass in the marathon runners