Magnetic resonance imaging (MRI) has major contribution in early diagnosis of ankylosing spondylitis (AS). As it is difficult to determine disease activity owing to the lack of close relation between laboratory tests, clinical findings and imaging, MRI has been used as an objective outcome measure. The aim of this study is to investigate the relation between spinal MRI findings with disease activity and other outcome measures. Fifty patients fulfilling modified New York criteria for AS were enrolled to the study. All the patients were evaluated with Bath AS Disease Activity Index (BASDAI), AS Disease Activity Score (ASDAS), Bath AS Functional Index (BASFI), Bath AS Metrology Index (BASMI), Bath AS Radiology Index (BASRI) and As Quality of Life. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were measured as laboratory parameters, and ASspiMR scores were determined by spinal MRI. The median total ASspiMR-a score was 5.2. Spinal inflammation was evaluated in spinal segments, and thoracic segments had the highest mean ASspiMR-a level (3.1 ± 5.94). Cervical and lumbar ASspiMR were correlated with only BASRI, and total ASspiMR score was correlated with BASRI, BASMI and CRP. Thoracic ASspiMR score was correlated with patient's and doctor's global assessments, BASFI, BASMI, BASRI, ASDAS A, ASDAS B, ASDAS C, ASDAS D, ESR and CRP (P < 0.05). According to our results, the thoracic spine was the most related region with disease activity parameters and clinical outcome measures, so we suggest thoracic spine MRI evaluation in order to determine the disease activity.