Tenoxicam is a thienothiazine derivative with anti-inflammatory properties. Due to its long half-life (40-90 hours) the drug can be administered once daily. One-hundred patients with tendinitis or bursitis were allocated in a double-blind study comparing 20 mg of tenoxicam to 20 mg of piroxicam. Both drugs were administered once daily for a period of 15 days. Clinical evaluations were performed before, on the third and seventh days of therapy and after treatment. The parameters evaluated were: spontaneous pain, tenderness, pain on movement, swelling and functional limitation. Laboratory examinations were performed prior to and at the end of the therapy. Efficacy was considered excellent or good in 42 patients of each group, moderate in six treated with tenoxicam and in four with piroxicam and poor in two with tenoxicam and four with piroxicam. Statistical evaluation was based on the Wilcoxon and U-test. No significant differences were observed between the groups. Nausea of mild intensity occurred in four cases of the tenoxicam group and in one of the piroxicam group.