The objective of this article is to evaluate different T-score cut-off points in the calcaneus in order to establish the prevalence of osteoporosis in the general population and to evaluate the clinical value of bone mineral density at the calcaneus as a tool to identify patients with spine or hip osteoporosis. A total of 1455 people (727 women and 728 men) from the Hortega cohort were studied. The densitometric studies were carried out in the calcaneal region using a Peripheral Instantaneous X-ray Imaging (PIXI) Lunar bone densitometer. We established three cut-off points (-1.6, -2.0, -2.5). One-hundred twenty-five patients (67 men with a mean age of 47 +/- 13 yr and 58 women with a mean age of 66 +/- 8 yr) from internal medicine outpatient clinics who were undergoing densitometry of the calcaneus, spine, and hip were subsequently studied. The prevalence of osteoporosis in women with a calcaneus T-score -1.6 was 12.4%, which is comparable to the 12.7% obtained with an axial densitometer in a Spanish population. The prevalence in men was 7.8%, with a calcaneus T-score of <-2.0. In women, the highest sensitivity (85%) was obtained with a calcaneus T-score of <-1.0 and the highest specificity with a calcaneus T-score of <-2.5. In men, the best sensitivity (61%) was obtained with a calcaneus T-score of <-1.0 and the best specificity (98%) with a calcaneus T-score of <-2.5. A calcaneus T-score <-1.6 is an adequate cut-off to establish the prevalence of osteoporosis in population studies. In women, a calcaneus T-score of >-1.0 enables the diagnosis of the disease to be excluded, whereas a calcaneus T-score of <-2.5 enables the diagnosis to be confirmed and treatment to be initiated in both men and women.