Bone mineral content (BMC) was determined by photon absorptiometry and cortical width (CW) by radiographic morphometry at two levels in 17 radii obtained postmortem from women ranging in age from 39 to 95 years. One level was the region in which Colles' fracture occurs (lower level) and the other about 6 cm from the styloid tip (upper level). Principal compressive strain at a 600-N load, fracture load, compliance, and work/unit length to fracture were measured in longitudinal compression tests. In general, BMC provides more precise estimates of mechanical properties than CW. The correlation coefficient between fracture load and BMC at the lower level was +0.83 (less than 0.001). Between work/unit length to fracture and BMC the coefficient was +0.81 (p less than 0.001).