1 Isoxicam, 200 mg once daily, was compared to ketoprofen, 100 mg three times daily, in 19 patients (16 males, three females) with ankylosing spondylitis in a 30-day, double-blind study conducted in two centres. 2 Improvements from baseline to final assessment were noted after both isoxicam and ketoprofen in most clinical variables, with isoxicam, in general, being more effective than ketoprofen. 3 Isoxicam was significantly superior to ketoprofen in reducing pain and was judged by both patients and physicians to be superior overall to ketoprofen. 4 Of the 13 patients who expressed a preference, 10 preferred isoxicam. 5 Typical NSAID side effects were encountered with both drugs.