A standard fixed dosing regimen (S) and a variable dosing regimen (VD) of naproxen for patients with knee and hip osteoarthritis were compared in a multicentre, open, controlled, parallel 8-week trial. The daily dose of naproxen (Naprosyn) in the S-group was 500-1000 mg, in VD maximum daily dose was 1000 mg. The number of patients entering the study was 396 (286 females). Mean (SD) age was 67 (10) and 67 (11) years in the S- and VD-groups respectively. The number of patients available for efficacy analyses, including the withdrawals, was 356. Efficacy measures included pain on movement, night pain, morning stiffness, a functional index and patient's and doctor's overall assessments. Similar improvement was seen in both groups. The number of patients withdrawn due to adverse reactions in S and VD was 35 and 23 respectively (p less than 0.05). Group differences in drug consumption were highly significant (p less than 0.01) with a 20-30% lower consumption in the VD-group. Thus, similar efficacy and possibly better tolerance was obtained with a lower drug consumption by a variable dosing regimen compared to a fixed regimen.