Summary In order to assess the potential role of lipoprotein (a) as a risk factor for cardiovascular disease in diabetes mellitus, plasma concentrations were measured in a large group (n = 500) of non-insulin-dependent (NIDDM, n = 355) and insulin-dependent (IDDM, n = 145) patients. Concentrations of lipoprotein (a) were compared in diabetic patients with (n = 153) or without (347) documented vascular disease (ischaemic heart disease, peripheral vascular disease or macroangiopathy). They were significantly higher (p 0.05) in patients with ischaemic heart disease (mean [interquartile range] 15.5 (5.038.0) vs 9.0 (4.526.0) mg/dl) or macroangiopathy (13.0 (5.038.0) vs 9.0 (4.025.0) mg/dl) compared to patients without manifestations of vascular disease. In addition, stepwise logistic regression analysis identified lipoprotein (a) levels 30 mg/dl as being independently associated with the presence of cardiovascular disease. Lipoprotein (a) was an independent risk factor for ischaemic heart disease and macroangiopathy in this group of IDDM and NIDDM patients. [Diabetologia (1995) 38: 711714]