A 14-day double-blind clinical study was conducted on 16 patients with clinically active rheumatoid arthritis to compare the effects of etodolac (600 mg daily) and diclofenac (150 mg daily). Admission criteria were: functional impairment between Steinbrocker's classes I to III, Ritchie's index greater than 10 and erythrocyte sedimentation rate greater than 25 mm/h, and finally active involvement of the small joints of the hands. Following a wash-out period of at least two days from their previous non-steroidal anti-inflammatory drugs, trial patients received etodolac or diclofenac for five consecutive days by random allocation; after that, and after another two day wash-out period, all patients were crossed-over to the alternate drug for another five consecutive days. One day before intake and on the last day of each treatment lap, each patient was examined in regard to the circadian grip strength (of the more severely affected hand), Ritchie's index and acute phase reactants; at the end of the second treatment period, subjective drug preference was explored. Grip strength was assessed by the patients themselves with a dynamometer at 08h00 and every two hours thereafter until 20h00. The overall daily value was calculated by measuring the area under curve (AUC) depicting the grip strength profile. Both groups of patients showed significant improvement of the Ritchie's index (p less than 0.01) and grip strength AUC (p less than 0.05), while taking medication, whereas no significant variations were noted in regard to the values of the acute phase parameters both between the two treatment groups, and within each treatment group. At termination, four patients expressed preference for etodolac, eight were in favour of diclofenac, and four gave an indifferent judgement. No statistically significant differences were detected between the two treatment groups; also no adverse events were seen in this short-term study. The results confirm the effectiveness and tolerability of etodolac in the acute stage of rheumatoid arthritis.