Assessment of roentgenographic measurements of cortical bone of the radius in 196 elderly females, including 63 diabetics, revealed that: (1) in the non-diabetic group there was a significant loss of cortical bone relative to the number of years after the menopause and to body weight; (2) although there was a significant loss of cortical bone relative to years postmenopausal in a group of diabetic patients the cortex in the diabetic group was better preserved than in those non-diabetic controls in whom no vertebral compressions were diagnosed in the roentgenograms; no correlation between bone loss and body weight was found among the diabetics; (3) the thinnest cortical bone and the lowest average body weight was found in the 34 non-diabetics with vertebral compression deformities. It thus appears that involutional osteoporosis will be less prevalent among old women suffering from diabetes mellitus than in comparable non-diabetic subjects, and more prevalent among non-diabetics of low body weight than in old women who are obese or of normal weight.