1. The mean attenuation coefficients of trabecular and cortical bone in the radius were measured in 32 female patients with fractured proximal femur, and in 28 age-matched female controls, with a special-purpose computed tomography-scanner. 2. The largest difference between the two groups was in the mean attenuation coefficients for trabecular bone in the distal radius. The mean value for fracture patients (0.53 cm-1) was significantly lower (P < 0.02) than the mean value for the controls (0.62 cm-1). These results are consistent with the view that a loss of trabecular bone predisposes to fractures of the proximal femur.