Background: Spondyloarthritis (SpA) traditionally encompasses ankylosing spondylitis, psoriatic arthritis and reactive arthritis associated with inflammatory bowel diseases. Sacroiliac joint (SIJ) inflammation is an important and usually the first finding of SpA. Objectives: The aim of this retrospective study was to assess the value of different magnetic resonance imaging (MRI) sequences in evaluation of bone marrow and subchondral bone changes in active sacroiliitis and inter-and intra-observer reliability of these sequences. Patients and Methods: Ninety patients (65 males, 25 females; meanage 33.44 +/- 11 years; range 15 to 62) withMRIfindings suggestive of active sacroiliitis were selected from picture archive and communication system (PACS) by the consensus of two radiologists. The SIJs were retrospectively analyzed by two radiologists separately blinded to each other's evaluations. Each sequence was evaluated at different times (one week apart from each other) in the same monitor of PACS system by each observer. Periarticular bone edema and contrast enhancement were recorded separately by each observer. Results: Highest agreement between measurements of observer 1 and 2 was found on contrast enhanced fat suppressed T1 weighted imaging (CE FS T1 WI) (97.78%) among all sequences and on FS T2 WI of axial planes within sequences taken before contrast injections (97.78%). Conclusion: FS T2Wand CE FS T1Wsequences of axial planes were the most useful sequences in determination of active sacroiliitis. Therefore, in patients with renal failure or allergy to contrast media, FS T2 WI can be obtained to detect active sacroiliitis.