Flurbiprofen (150-200 mg daily) and phenylbutazone (300-400 mg daily) were compared in the management of 27 patients with active ankylosing spondylitis. This was a parallel, double-blind, and randomized trial of 6 weeks duration. Both drugs were equally effective in the relief of pain and tenderness of the affected joints. Overall subjective improvement, assessed by the patient and the investigator at the end of the trial, favored phenylbutazone, but it did not reach a statistically significant level. The mean values of the endpoint parameters of spinal motion showed statistically significant improvement in both groups, except in the Schober test in the flurbiprofen group and chest expansion in the phenylbutazone group. Untoward effects characteristic of these drugs were found in a few patients.