The aim of this study was to compare bone mineral density (BMD) in a population-based sample of middle-aged and older Norwegians, with reference values provided by the manufacturer of the densitometer (Lunar) in order to evaluate whether these reference values are suitable for Norwegians. Additional aims were to estimate the prevalence of osteoporosis. Bone mineral density of the hip and total body was measured by dual-energy X-ray absorptiometry in 2303 men and 3105 women 47-50 and 71-75 years old, respectively, in western Norway, as part of the Hordaland Health Study (HUSK). Of these, 3403 white individuals were free of medications or diseases known to influence bone metabolism (reference group). Compared with the Lunar reference population, men and older women had a slightly but significantly lower BMD of trochanter and total femur and middle aged women had significantly higher total body BMD. Except for the higher mean BMD of total body among middle-aged women and the uniformly lower BMD values of Ward's triangle, the deviations from the reference values of the manufacturer were less than 4%. Approximately 2.6% of middle-aged men vs 0.9% of middle-aged women were classified as osteoporotic on the basis of BMD of femoral neck. While the BMD values for femoral neck in this healthy Norwegian population are similar to the reference population of Lunar, the values of trochanter and total femur are lower in all groups except middle-aged women; however, the discrepancies are not of sufficient magnitude to warrant rejection of this commonly used database among Norwegians. Use of the young adult means from the Lunar reference database classified a higher proportion of middle-aged men than women as osteoporotic and osteopenic.