Objective. To determine a bone mineral density (BMD) changes in patients with ankylosing spondylitis (AS) depending on demographical data, clinical and laboratory findings. Materials and methods. 42 patients (male - 36 (85,7%), female - 6 (14,3%), 21 to 47 years of age, mean age 33,2±8,4, mean disease duration 7,8±5,9 years) with proven diagnosis of AS were included in the study performed at the Centre of osteoporosis treatment and prevention. All patients were HLA-B27 positive, 23 (54,8%) had peripheral arthritis. Evaluation included back pain assessment with VAS scale, morning stiffness duration assessment, modified Schober’s test, limitation of chest expansion assessment, calculation of BASDAI, BASFI and ASDAS-CRP scores, ESR and CRP levels. To evaluate BMD all patient underwent dual-emission X-ray absorptiometry (DXA) at lumbar spine (L1-L4) and hip neck. Results. Among male patients normal BMD was found in 6 (16,7%) patients, 19 (52,8%) had osteopenia, 11 (30,5%) -osteoporosis. Among male patients normal BMD was found in 1 (16,7%) patients, 1 (16,7%) had osteopenia, 4 (66,6°%) — osteoporosis. BMD at the lumbar spine in male patients was significantly higher compared to females (p<0,05). Patients with high disease activity and peripheral arthritis had significantly lower BMD at lumbar spine. Patients with osteoporosis and osteopenia had higher pain score on VAS compared to patients with normal BMD. We observed an association between BMD and duration of AS, Schober’s test results, disease activity and CRP. Conclusion. High clinical activity, presence of peripheral arthritis, significant changes in spinal movement were found to be predictors of BMD decrease in patients with AS. Patients with AS and osteopenia had more pronounced pain syndrome.