Bone density and mass related values were determined in femoral condyles and in the second lumbar vertebra in males of middle age. A poor agreement was found between measurements in the two locations. The measurements were compared with age and body size by means of correlation analysis and multiple regression analysis. There was a significant linear relationship between lumbar measures and age (beta coefficient -0.61 and -0.75) while the relationship with age for the femoral measures was less (beta -0.36 and -0.45). For all measurements there was a poor correlation with body size (weight, length and surface area). Bone mineral content measurements in the lumbar and appendicular skeleton have different clinical implications. When selecting a method for estimating the bone mineral content careful attention must be paid to what type of information is wanted and whether the method is adequate for that particular purpose.