Some studies have reported low bone mineral density (BMD) in patients with Addison's disease, whereas others have found BMD to be normal. It is possible that over-replacement of corticosteroids and adrenal androgen deficiency may contribute to a reduction in BMD in these patients. The aims of this study were to examine BMD using dual-energy X-ray absorptiometry in patients with treated Addison's disease at multiple skeletal sites and to investigate the relationships between these measurements and corticosteroid dose. Nineteen men, 3 premenopausal and 7 postmenopausal women with Addison's disease were studied and data from these patients were analyzed separately and as a group. The mean SEM age and duration of Addison's disease of the men were 44 +/- 3.8 years and 15 +/- 2.2 years, in the premenopausal women 40 +/- 2 years and 5 +/- 2.4 years, and in the postmenopausal women 68 +/- 4 years and 20 +/- 5 years, respectively. Eight men were unexpectedly hypogonadal (serum testosterone <13 nmol/l). BMD was expressed as a percent of values in normal controls (n = 418) adjusted for age, sex, ethnic origin, menopausal status and body weight. In the whole group (n = 29), mean BMD of the patients with Addison's disease was not different from normal at any site [mean (+/- SEM) lumbar spine 99.5% +/- 2.9%; femoral neck 99.3% +/- 2.5%; Ward's triangle 96.2% +/- 3.5%; trochanter 99.2% +/- 2.9%; radius 99.8% +/- 2.1%; total body 98.5% +/- 1.4%]. However, there was a wide range of bone densities, with some patients having a low BMD at multiple sites. Bone density was negatively correlated with current and cumulative corticosteroid dose per kilogram body weight and duration of Addison's disease. In conclusion, BMD in patients with Addison's disease is little different from normal, but may be lower in patients with disease of long duration and a high cumulative corticosteroid dose. Unexpected hypogonadism in men with Addison's disease is common.