Tenoxicam (20 mg/day) and piroxicam (20 mg/day) were compared in a double-blind, parallel group study over 4 weeks in 30 patients with ankylosing spondylitis. Both tenoxicam and piroxicam reduced spinal pain, but the improvement was greater with piroxicam. Tenoxicam and piroxicam were equally effective at improving duration of morning stiffness. Slight improvement was seen with other symptoms with both treatments. Patients were slightly more tolerant of piroxicam than tenoxicam and most patients elected to continue on their particular therapy at the end of the study.