The clinical course of a patient with acute lymphoid immunoblastic leukaemia and prominent nodular haemorrhagic skin lesions is described. Cytological, cytochemical and electronmicroscopic studies were performed on bone marrow and skin blast cells. The absence of surface immunoglobulins and of the other markers for B lymphocytes (EA and EAC rosettes) and the presence of 30% of spontaneous sheep erythrocyte rosettes excluding an acute leukaemia with Burkitt's tumour cells, suggest that T cells are involved. Complete haematological and cutaneous remission was obtained with prednisone therapy.