OBJECTIVE The aim of this study was to determine bone mineral density (BMD), markers of bone metabolism, fractures, and steroids reflecting hormonal control in adult males with congenital adrenal hyperplasia (CAH). SUBJECTS, METHODS, AND DESIGN: We compared CAH males with 21-hydroxylase deficiency (n=30), 19-67 years old, with age- and sex-matched controls (n=32). Subgroups of CYP21A2 genotypes, age, glucocorticoid preparation, poor control vs overtreatment, and early vs late (>36 months) diagnosis were studied. BMD measured by dual energy X-ray absorptiometry and markers of bone metabolism and androgens/17-hydroxyprogesterone levels were investigated. RESULTS All, including older (>30 years), CAH patients had lower BMD in all measured sites compared with control subjects. The null group demonstrated lower BMD in more locations than the other groups. Osteoporosis/osteopenia was present in 81% of CAH patients compared with 32% in controls (≥30 years). Fracture frequency was similar, osteocalcin was lower, and fewer patients than controls had vitamin D insufficiency. IGF1 was elevated in the milder genotypes. In patients, total body BMD was positively correlated to weight, BMI, total lean body mass, and triglycerides, and negatively to prolactin. Patients on prednisolone had lower BMD and osteocalcin levels than those on hydrocortisone/cortisone acetate. Patients with poor control had higher femoral neck BMD. There were no differences in BMD between patients with an early vs late diagnosis. CONCLUSIONS CAH males have low BMD and bone formation markers. BMD should be monitored, adequate prophylaxis and treatment established, and glucocorticoid doses optimized to minimize the risk of future fractures.