Thirty six patients with chronic glomerulonephritis, 35 -- with chronic pyelonephritis, 5 -- with diffuse glomerulonephritis with systemic lupus erythematosus and 60 healthy subjects were examined with the method by sedimentation with 3.5 per cent solution of polyethyleneglycol for the determination of circulating immune complexes. The average value for the healthy subjects is X = 0.123 +/- 0.047 mg/ml. The average value plus two standard deviations = 0.217 mg/ml is accepted as normal in healthy subjects. An elevated level of circulating immune complexes is found in 60 per cent of the patients with lupus nephritis and 25 per cent of the patients with chronic glomerulonephritis. The average values for the last two groups are X = 0.475 +/- 0.554 mg/ml and X = 0.184 +/- 0.185 mg/ml respectively. Whereas in the patients with lupus nephritis the values for the single patients are considerably over the adopted norm, in patients with chronic glomerulonephritis, in the majority of the cases, they are about its upper limit.