Epidemiologic studies have identified lipoprotein(a) (Lp(a)) as an independent risk factor for atherosclerosis, mainly for coronary heart disease. Atherosclerosis is the most common cause of death in diabetic patients, but there is little information available concerning the importance of Lp(a) in these patients. We compared the presence or absence of late diabetic complications with Lp(a) serum concentrations in 224 patients (82 IDDM, 142 NIDDM). Lp(a) distribution was skewed as described for non-diabetic patients. Despite highly significant differences for total cholesterol, total triglycerides, HDL-cholesterol, VLDL-cholesterol and VLDL-triglycerides (P < 0.001) and for LDL-cholesterol (P < 0.01) Lp(a) concentrations were similar in NIDDM and IDDM (mean: 27 vs. 30, median: 12 vs. 21 mg/dl, P = 0.10). Diabetic polyneuropathy, autonomic neuropathy, nephropathy, peripheral occlusive disease, diabetic gangrene and coronary heart disease were not associated with raised Lp(a) values. Non-insulin-dependent patients with retinopathy exhibited higher Lp(a) concentrations in serum than those without this complication. This significant association was lost when duration of diabetes was taken into account by logistic regression. We conclude, that other risk factors surpass the significance of Lp(a) in diabetic patients.