Paraproteinaemia may be associated with xanthomatous skin deposits and these can arise in the absence of elevated lipid levels. Two cases of benign monoclonal gammopathy with diffuse plane xanthomatosis are reported. Case 1 exhibited hypolipidaemia and a functional deficiency of C1 esterase inhibitor. Case 2 showed a normal lipoprotein profile, abnormal platelet aggregation, and a cutaneous vasculitis with evidence of complement consumption via the classical pathway. The significance of these abnormalities is discussed.