increased index of suspicion will probably uncover more cases.I thank the physicians and surgeons of Aberdeen Royal Infirmary and the Royal Cornhill Hospital for access to clinical data.References Barker, C. S. (1945). Canadian Medical Association Journal, 52, 285. Bendit, M. (1945). British Medical Journal, 1, 664. Burt, C. A. V. (1931). Archives of Surgery, 22, 875. Egdell, R. W. and Johnson, W. D. (1973). American Journal of Obstetrics and Gynecology, 117, 1146. Ehrentheil, 0. F., and Wells, E. P. (1955 Journal, 1974, 4, 83-84 Skin lesions are frequent extracolonic manifestations of ulcerative colitis, the incidence of such lesions ranging from 6% to 34% of cases (Bockus et al., 1965 The second day after stopping the ooumarin the patient became feverish and developed painful blue spots on both thighs which disappeared spontaneously within a day. Two days later a more extensive bluish area appeared on the inner aspect of the left thigh which did not resolve but instead central haemorrhagic necrosis of the skin developed. Again extensive examination was carried out for a systemic disease but no specific abnormalities were found. Treatment with coumarin was reintroduced but was stopped after three days because of haematuria and bloody stools. At that time the patient also suffered a short-lasiting attack of arthritis of the jaw joints. X-ray studies of the thorax and colon and an intravenous pyelogram were thought to show nothing abnormal. At sigmoidoscopy the rectal mucosa appeared to be haemorrhagic.On 16 August two biopsy specimens were taken from indurated remnants of healed thrombophlebitis on the back of the left thigh and upper calf. That evening a large, painful, bluish skin discoloration appeared centred around the previous already necrotic lesion on the left thigh. On 18 August he was transferred to this hospital for investigation of blood-clotting abnormalities.On admission he appeared ill and ipale-looking. Temperature 38 9'C. Examination of the head, neck, lungs, and heart showed nothing abnormal. His abdomen was slightly tender on palpation but was otherwise normal. On the anterior aspect of the left thigh there was an extensive slightly raised area of bluish purple discoloration. The lesion was sharply and serpiginously circumscribed and surrounded by an erythematous zone. Small vesicles and a few blisters filled with haemorrhagic fluid were present within this area, which surrounded a centrolateral black necrotic patch ( fig. 1 a, b). The left side of the scrotum was black and necrotic and surrounded by an erythematous zone. All the peripheral arteries pulsated normally. Urine analysis and blood chemistry showed nothing abnormal thoughout the illness. The E.S.R. was 73 mm in the first hour, haemoglobin 9 g/ 100 ml, and W.B.C. 20,000/mm3. Fibrin