This study aims to examine the impact of long-term treatment with the anti-TNF antibody infliximab on radiographic progression of hip arthritis in ankylosing spondylitis. Anteroposterior X-rays of the pelvis obtained at baseline from consecutive patients with ankylosing spondylitis and bilateral hip arthritis were compared with X-rays obtained after 6 ± 2.5 years (mean ± SD) of continuous infliximab treatment. Analysis was performed by the Bath Ankylosing Spondylitis Radiology Hip Index (BASRI-h) scoring system (min 0, max 4). Hip joint space width was also assessed by the average of measurements at three distinct sites between the acetabulum and femoral head. In 23 patients with active disease (21 men, mean age and disease duration of 45 and 16 years, respectively), the BASRI-h score at baseline was 1 in 7, 2 in 16, 3 in 16, and 4 in 7 hips (including two arthroplasties). Individual BASRI-h scores at baseline (2.50 ± 0.86, mean ± SD) remained unchanged in all patients at end of follow-up. At baseline, the average width of the whole joint space (3.56 ± 0.70 mm, n = 44) was not associated with disease activity measurements but negatively correlated with BAS functional index (Spearman r = -0.5, P = 0.007). After 2-10 years of infliximab treatment, the average width of the whole joint space in these patients (3.59 ± 0.79 mm) was not reduced. These results suggest that radiographic progression of hip arthritis in ankylosing spondylitis may be arrested during infliximab treatment.