HISTORY AND CLINICAL FINDINGS: Two months after being diagnosed as having refractory anaemia with an excess of blasts in transformation (RAEB-T), a 62-year-old man presented in the emergency room with fever (40 degrees C) for two weeks and scattered deep-red macular indolent efflorescences over the chest, back, face and thighs. Other than splenomegaly there were no significant findings on physical examination. INVESTIGATIONS: Erythrocyte sedimentation rate was increased to 38 mm in the first hour. Haemoglobin concentration and platelet count were at the lower limits of normal, white cell count within the normal range. Differential count: 60 erythroblasts per 100 leukocytes and 33.5 blast cells. Two skin biopsies revealed massive oedema in the upper corium and focal erythrocyte extravasations. There were perivascular and perifollicular inflammatory infiltrates in the deeper layers and elastosis of the corium. There was no leukocytoclastic vasculitis. These findings established the diagnosis of Sweet syndrome and erythroleukaemia. TREATMENT AND COURSE: The erythroleukaemia was treated symptomatically and the skin changes gradually receded under prednisone, 1 mg/kg, but new spots occurred when the prednisone dose was halved. Candida oesophagitis occurred as a complication of the erythroleukaemia. Chest radiogram showed diffuse infiltrates in both upper lobes of the lung. Despite intensive antimycotic and antibiotic treatment the patient died 10 days later from pulmonary aspergillosis. CONCLUSION: This case report describes the rare occurrence of Sweet syndrome during the transformation from a myelodysplastic Syndrome to erythroleukaemia.