Insulin-dependent diabetic patients with nephropathy have a high risk of cardiovascular disease. Chronic inflammation is a part of the pathogenesis of atherosclerosis, and presently we have studied the relation between the inflammatory state, measured as levels of interleukin-6 and C-reactive protein and fibrinogen in diabetic nephropathy. Thirty-three insulin-dependent diabetic patients with diabetic nephropathy (urinary albumin excretion rate (AER) > 300 mg/24-h) and 22 patients with incipient diabetic nephropathy (AER 30-300 mg/24-h) were compared with 14 non-diabetic controls and 17 diabetic patients with normal AER (<30 mg/24-h). Fibrinogen was significantly higher in diabetic nephropathy than in non-diabetic controls and diabetic patients with normal AER (median 8.1, range (5.4-15.6) mu mol/l vs. 6.6 (5.0-12.1) mu mol/l, p < 0.05, and 6.2 (5.0-9.0) mu mol/l, p < 0.005, respectively), while C-reactive protein did not deviate between groups. Interleukin-6 was significantly elevated in all insulin-dependent diabetic patients (diabetic nephropathy (3.2 (1.0-14.5) pg/ml, p < 0.005), incipient nephropathy (3.7 (1.0-22.9) pg/ml, p < 0.005) and diabetic patients with normal AER (2.7 (1.0-9.0) pg/ml, p < 0.05) compared with nondiabetic controls (1.2 (1.0-6.2) pg/ml)). When fibrinogen was adjusted for interleukin-6, C-reactive protein or both, the level of fibrinogen was still higher in patients with diabetic nephropathy than in patients without nephropathy (p < 0.05), which suggests that inflammation is not the only mechanism that increases fibrinogen levels in patients with diabetic nephropathy.