The cases of two patients with chronic myelomonocytic leukaemia associated with periarteritis nodosa-like, antineutrophil cytoplasmic antibody negative, systemic vasculitis, are reported. A 61 year old man was admitted with fever, diffuse myalgia, and abdominal pain. Blood and bone marrow examination showed chronic myelomonocytic leukaemia. Vasculitis of the gall bladder was responsible for acalculous cholecystitis. A massive spontaneous bilateral perirenal haemorrhage occurred. A 73 year old woman with chronic myelomonocytic leukaemia had been followed up for one year when unexplained fever occurred. Two months after the onset of fever, sudden abdominal pain was ascribed to spontaneous bilateral renal haematoma related to bilateral renal arterial aneurysms. Neuromuscular biopsy showed non-necrotising periarteriolar inflammation. To our knowledge, systemic vasculitis has never been reported in chronic myelomonocytic leukaemia. In our two cases a non-random association is suggested because (a) chronic myelomonocytic leukaemia is a rare myelodysplastic syndrome, (b) spontaneous bilateral perirenal haematoma is not a usual feature of periarteritis nodosa.