There are few data concerning the occurrence of peak bone mass in women of South Asian origin. The aim of this study was to determine the level of peak bone mass in South Asian women in the UK and to determine whether any observed differences could be explained by differences in body size. Two groups of South Asian women, those of (1) Pakistani Muslim and (2) Gujarati Hindu origin, together with a European group aged 18 to 36 years, were recruited from primary-care population age-sex registers in the Greater Manchester area. They were invited to attend for a detailed interview-assisted lifestyle questionnaire and assessment of height and weight. Bone mass density (BMD) at the hip and lumbar spine was measured by dual energy X-ray absorptiometry (DEXA) scan (Hologic QDR 4500). Volumetric bone density was measured at the distal radius using pQCT (Norland Stratec XCT 2000). Linear regression was used to determine whether any observed differences in the level of bone mass could be explained by differences in body size. A total of 119 European women with a mean age of 30.4 years, 98 Pakistani Muslim women with a mean age of 29.2 years and 20 Gujarati Hindu women with a mean age of 29.2 years had bone density measurements performed. The Europeans were taller and heavier than either South Asian group. Peak BMD was greater among the European than the Pakistani women at all three measuring sites, with the Gujarati women having intermediate values at the hip and lumbar spine. Observed differences disappeared, however, after adjusting for height and weight. There were no differences in volumetric density at the lumbar spine or distal radius between the groups. In summary, there are differences in the level of bone mass between European and South Asian women, though these can be explained by differences in bone size, height or weight. © International Osteoporosis Foundation and National Osteoporosis Foundation 2005.