Thrombophlebitis migrans complicating ulcerative colitis has been reported only once previously when it occurred in a patient with chronic and extensive bowel disease. This report describes the occurrence of thrombophlebitis before any bowel upset in a patient who proved to have only a mild colitis, and no laboratory evidence of hypercoagulability. It seems that thrombophlebitis migrans is a further systemic complication of ulcerative colitis, and that its occurrence may precede overt bowel disease.