Thirty-six patients with active rheumatoid arthritis were treated in a double-blind cross-over study of phase-release aspirin tablets and aspirin B. P. tablest. Twenty-nine patients completed the study. The phase-release preparation given twice daily proved as effective as aspirin B.P. given four times daily. Better results were produced by the phase-release aspirin in respect of the degree and duration of morning stiffness, grip strength and joint size, although the differences did not reach the level of statistical significance. The E.S.R. was significantly reduced by the B. P. preparation but this result was thought to be due to an order effect in the weeks of therapy.