We studied the occurrence of osteopenia, as reflected by decreased cortical bone thickness, in a nonobese animal model of hereditary non-insulin-dependent diabetes with long duration, i.e., 8-month-old Goto-Kakizaki (GK) rats. In addition, motor nerve-conduction velocity was measured in the GK rats. Age- and weight-matched Wistar rats served as controls. The GK rats displayed marked glucose intolerance, as compared to control rats, in an intraperitoneal glucose tolerance test. Decreased cortical bone thickness by approximately 15%, was evident in X-ray analysis of metatarsal bones (p < 0.001) and humerus (p < 0.05) of the GK rats. Motor nerve-conduction velocity, measured in the sciatic nerve, was also decreased (by 10%) in the GK as compared with the age-matched control rats (p < 0.05). In conclusion, reduction of cortical bone thickness is present in 8-month-old GK rats, which simultaneously demonstrate signs of peripheral neuropathy. Thus, the GK rat appears to be a model of NIDDM suitable for studies of diabetic bone disease in the absence of obesity.