Urinary excretions of albumin, glycosaminoglycans (GAGS), total sialic acid (TSA), and lipid associated sialic acid (LASA) were measured in 78 non-insulin dependent diabetic patients (NIDDM) and 28 healthy subjects. TSA excretion was significantly higher in normoalbuminuric and microalbuminuric diabetic subjects than the control subjects and TSA excretion was correlated with urinary albumin excretion rate (AER). In normoalbuminuric diabetics, the duration of diabetes correlated significantly with both sialicaciduria and albuminuria. Although serum TSA levels were significantly higher in both diabetic groups than the control subjects, there was no correlation between serum and urinary TSA levels.