The objective of the study was to elucidate if individuals with Down's syndrome (DS) are likely to experience an increased risk of osteoporosis with advancing age, in addition to precocious aging and their skeletal anomalies. Bone mineral density (BMD) was measured in 22 home-reared adults (9 males and 13 females; age 26.22 +/- 4.45 and 23.65 +/- 3.23 years, respectively) by dual energy X-ray absorptiometry (DXA). The BMD of the second to fourth lumbar vertebrae was measured in posteroanterior projection and the mean density expressed as grams per square centimetre. The BMD of DS individuals was compared with 27 control subjects (12 males and 15 females) of the same age (age 24.16 +/- 3.46 and 23.86 +/- 2.92 years, respectively). The results showed that the BMD of the lumbar spine in the males as well as in the females with DS was significantly lower than that in their control counter-parts (p < 0.001). Comparing the DS males with the females, the BMD was lower in the males at a level of 9%. Factors that contribute to this disorder may be mainly the muscular hypotonia, the sedentary life-style and the accompanying diseases which frequently observed in the syndrome. Future studies must be focused on the biochemistry of bone metabolism, the evaluation of gonadal, thyroid and parathyroid function, and the genes of the extra chromosome 21.