Total sialic acid (TSA) and lipid-associated sialic acid (LASA) concentrations were found to be significantly elevated in the sera of patients with chronic glomerulonephritis (CGN) and those with chronic renal failure (CRF) who were maintained on haemodialysis. The reference values for TSA and LASA were determined in the sera of 60 healthy subjects (33 males and 27 females) and showed no significant dependence on age and sex. No correlation existed between the TSA and LASA values, nor between TSA and LASA and the serum BUN and creatinine values in the patients and controls. A large amount of bound sialic acids was excreted in the urine of both groups of patients, although the serum sialic acid levels were increased.