A double-blind, cross-over comparison of Naprosyn (naproxen) 750 mg daily and Butacote (enteric-coated phenylbutazone) 300 mg daily was carried out in a multi-centre trial. Twenty-five patients, mostly male and under 40 years of age, were entered. After a 2-week period in which any existing anti-inflammatory drugs were tailed off, patients were entered into the trial and treated for 1 month with each drug. Patients were assessed at 4-weekly intervals. Both drugs significantly reduced morning stiffness. Morning pain and discomfort and wall-tragus distance were also significantly reduced by both drugs during the trial. Results of the Schober test showed improvement during both treatment periods. There were no overall statistically significant differences between the effects of the 2 drugs on objective parameters. However, overall subjective assessment of symptoms showed a greater improvement on Butacote. Treatment preferences by physician and subjective assessment by the patient both favoured Butacote but the difference between the 2 drugs was not statistically significant. Side effects were mostly of a minor nature. One patient had to discontinue the trial, due to indigestion while taking Butacote.