Forty-five patients with definite or classical rheumatoid arthritis were randomly allocated into two groups and treated with piroxicam 20 mg once daily or naproxen 250 mg twice daily in a 3-month, double-blind study. The results were available in 38 patients (21 in the piroxicam group and 17 in the naproxen group). Both drugs showed significant effects on the majority of clinical parameters compared to baseline. However, piroxicam was significantly superior to naproxen in reducing the grade of swollen joints. Moreover, piroxicam had better efficacy as shown by the number of patients who preferred it to previous therapy; 13 (62% of the patients entered) compared to 8 patients (47%) who preferred naproxen. Tolerance of the two drugs was similar. Two patients in each group dropped out due to side-effects.