Phenylbutazone was used in the treatment of 40 patients with thrombophlebitis. The usual dosage schedule was 200 mg. by mouth thrice daily for three days and then 100 mg. thrice daily for four days. In each case the pain, swelling, and redness, and much of the induration, subsided promptly. The effects of the drug are illustrated by case histories of two men aged 20 and 27 years and a woman aged 27, chosen from the more difficult cases. Residual postphlebitic symptoms sometimes had to be controlled by the wearing of elastic stockings. No unfavorable side-effects from the drug were observed in any case.