We have previously shown considerable between-center variation in bone mineral density (BMD) in the 13 EVOS centers that performed bone densitometry on their sex- and age-stratified population samples, after adjusting for weight and age. We have now investigated whether part of the between-center variability may be attributed to between-center variations in the use of medications. Information was collected from 2088 women and 1908 men at baseline on whether the subjects had ever been prescribed calcium, calcitonin, anabolic steroids, fluoride, vitamin D, or glucocorticoids and, for the women, whether they had ever used the oral contraceptive pill (OCP) or hormone replacement therapy (HRT). Each of these variables was fitted into a regression model adjusted for age, height, weight, and center. Only OCP and HRT significantly affected BMD. Those who had ever used OCPs had spinal BMD 0.029 g/cm2 greater than those who had never used them. Users of HRT had higher BMD than nonusers: 0. 037 g/cm2 at the spine, 0.018 g/cm2 at the trochanter, and 0.018 g/cm2 at the femoral neck. As expected, there was a great variation between centers in the use of OCP and HRT, but there were no significant correlations between mean BMD at any site in a given center and the prevalence of OCP or HRT use in that center. The between-center variance in BMD at all three sites remained highly significant after adjusting for treatment (P < 0.001). We conclude that HRT and OCP use are associated with moderate increases in BMD. The geographical variability of BMD in Europe was not explained by treatment with pharmaceuticals.