Studied was the peripheral bone density of 39 women (ages 18 to 43) with the diagnosis of secondary amenorrhea in an effort to define the population of amenorrheic women at risk for osteoporosis. Eight women had exercise-induced amenorrhea (athletes), 20 women had amenorrhea associated with weight loss, and 11 women had premature menopause. These diagnoses were made on the basis of history, physical examination, and luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin levels, and failure to have withdrawal bleeding after the administration of progestin. Twenty-five nonathletic, normally menstruating women served as control subjects. The peripheral bone density of the amenorrheic athletes (0.738 g/cm2± 0.047) was not significantly different from that of the controls (0.726 g/cm2± 0.044). The average bone density of the group with weight loss-associated amenorrhea (0.672 g/cm2± 0.066) was significantly less than controls (P<.005) as was that of the women with premature menopause (0.616 g/cm2± 0.048,P<.001). There was a significant correlation between months of amenorrhea and decrease in bone density (r=0.506,P<.001). From this study it was concluded that women with exercise-associated amenorrhea are not at significant risk for cortical bone loss as measured by direct photon absorptiometry. Women with weight loss-associated amenorrhea and women with premature menopause are at significant risk for bone loss when compared with normal controls.