A single sympathetic block produced complete relief of pain in 90.1 per cent of a series of cases of thrombophlebitis; a second block relieved pain in the remainder. Phlebothrombosis, the other major type of venous thrombosis, is more difficult to diagnose ad is potentially fatal. It is more common among nonsurgical patients than among surgical ones. It demands immediate treatment to prevent fatal embolism. In the author's opinion, the diagnosis of phlebothrombosis takes precedence over every other emergency except massive bleeding. Placing a ligature between the clot and the heart is the only effective means of preventing fatal embolism.