The past 18 months have seen multireader validation exercises assessing the reliability and discriminatory properties of MRI, longitudinal data evaluating the prognostic significance of lesions observed on MRI, and data from clinical trials assessing the predictive capacity of MRI for major clinical response. Studies using new MRI-based technologies in ankylosing spondylitis have also been described.The reliability and discrimination of scoring systems for both sacroiliac joint and spinal inflammation using MRI are now sufficiently well validated to be used in the short-term clinical trial assessment of the anti-inflammatory efficacy of novel therapeutic agents. The finding of inflammatory lesions on MRI is also of prognostic significance for structural damage. MRI examination contributes to clinical and laboratory evaluation in the selection of patients likely to respond to antitumor necrosis factor agents. Newer MRI-based techniques such as whole-body MRI permit a broader scope of diagnostic ascertainment.MRI continues to assume an increasingly important role in the diagnostic, prognostic, and therapeutic assessment of patients with ankylosing spondylitis.