The purpose of this study is to evaluate bone mineral density (BMD) and bone turnover markers in men with ankylosing spondylitis (AS) and to determine their relationship with clinical features and disease activity. Serum carboxi terminal cross-linked telopeptide of type I collagen (CTX), osteocalcin (OC) levels, and BMD of lumbar spine and proximal femur were evaluated in 44 males with AS, 18-60 years of age, and compared with those of 39 age-matched healthy men. Men with AS had a significantly lower BMD at the femoral neck and total hip as compared to age-matched controls (all p<0.01). Osteopaenia or osteoporosis was found in 59.5% AS patients at the lumbar spine and in 47.7% at the femoral neck. Mean serum levels of OC and CTX were similar in AS patients and controls. There were no significant differences in BMD and bone turnover markers when comparing subgroups stratified according to disease duration or presence of peripheral arthritis. No correlations were found between disease activity markers and BMD or OC and CTX. In a cohort of relatively young males with AS, we found a high incidence of osteopaenia and osteoporosis. Disease activity and duration did not show any significant influence on BMD or serum levels of OC and CTX.