Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) is the most frequently used ankylosing spondylitis activity assesment by which through 6 questions 5 basic diseases symptoms (fatigue, back pain, joint pain/swelling, enthesitic points, intensity and duration of morning stiffness) are being evaluated. In distinction from mentioned, Ankylosing Spondylitis Disease Activity Score (ASDAS) is the first validated index for the AS activity assessment with the patient's assessments of the disease symptoms (back pain, duration of the morning stiffess, activity of the disease, pains and swelling of the peripheral joints) includes the acute phase reactants (SE or CRP). We compared BASDAI and ASDAS indexes to the group of patients with the AS, in order to evaluate their congruence and to evaluate the inluence of SE, fatigue and back pain at obtained values. The cross-sectional study was performed in a group of 36 patients with the AS whose disease activity levels were evaluated by the BASDAI and ASDAS (SE) index. Statistical data analysis was performed by Student t-test and frequency tables for non-parameter data. As it has been expected the significant correlation between BASDAI and ASDAS indexes has been confirmed (r=0.796; p=0.00). BASDAI/ASDAS average value of all of the patients was 4.2/2.8. From 36 patients with the AS according to the BASDAI index 42% had mild active disease (BASDAI <4), while according to ASDAS index 44% patients had very active disease (ASDAS 2.1-.5.3). Higher activity of the disease according to ASDAS index is the result of the elevated sedimentation which is assessed only in ASDAS index. Patients with higher BASDAI index statistically have more significantly expressed fatigue and spinal pain without statistically significant difference in sedimentation (p=0.120). Examinees with higher ASDAS index have also significantly more expressed fatigue and back pain, but unlike BASDAI they have sedimentation (p=0.001). ASDAS is more recent clinical indicator of the AS activities which could be compared to BASDAI instrument. In this group of patients ASDAS seems to be more sensitive index because it discriminates more patients with the active disease.