Type 1 (insulin-dependent) diabetic patients with clinical nephropathy have a more than ten-fold increase in mortality of cardiovascular diseases compared with diabetic patients without nephropathy. The risk factors for cardiovascular disease, plasma concentrations of lipoproteins and fibrinogen, were investigated in 74 long-term diabetic patients: 37 with normal urinary albumin excretion, 20 with incipient nephropathy and 17 with overt clinical nephropathy based on urinary albumin excretion. The groups were matched according to sex, age and diabetes duration. The concentration of plasma cholesterol, very low density lipoprotein cholesterol, low density lipoprotein cholesterol, triglyceride and fibrinogen rose with increasing urinary albumin excretion. The plasma concentrations of these lipoproteins and fibrinogen were 11-14% higher in the patients with incipient nephropathy and 26-87% higher in the patients with overt clinical nephropathy compared with the patients without nephropathy. The plasma concentration of high density lipoprotein cholesterol was unaffected by albuminuria. Patients with normal urinary albumin excretion and HbA1c greater than 8.0% had significantly higher very low density lipoprotein- and lower high density lipoprotein cholesterol concentrations compared with patients with HbA1c less than 8.0%. Simple addition of the described risk factors can only account for a minor part of the greatly increased cardiovascular mortality in patients with diabetic nephropathy. An additional and possibly more decisive factor might be a change in the arterial wall, a change which promotes lipid accumulation and/or facilitates thrombus formation.