Fibronectins are adhesive proteins considered as markers of endothelial activation. Plasma fibronectin levels in diabetes mellitus (DM) have been found to be associated with atherosclerotic risk factors. This study was carried out to investigate plasma fibronectin and its relation with serum lipids, apolipoproteins AI, B100 and lp(a) in diabetic children. 35 children (19F/16M) with type I DM and 30 non-diabetic age and gender-matched controls were enrolled. Apolipoprotein and fibronectin concentrations were determined with nephelometric methods. Plasma fibronectin levels of the children with type I DM and the control group are not statistically different. HbA1c and triglycerides concentration are found to be significant predictors of plasma fibronectin in diabetic children, while effect of plasma cholesterol, apolipoprotein AI, B100 and lp(a) are insignificant. Diabetic children with triglycerides 1.13 mmol/l have elevated plasma fibronectin (median, 25th-75th percentiles; 29.6, 8.3-40.8 mg/dL) compared to the diabetic > or = 19.9, 8.6-30.7 mg/dL, p < 0.05) and non-diabetic children (16.6, 12.7-32.4 mg/dL, p < 0.01) with triglycerides < 1.13 mmol/L. On the other hand plasma fibronectin concentrations of diabetic and non-diabetic children with high triglycerides are not significantly different. In conclusion our data does not support the concept that plasma fibronectin is elevated in type I diabetes mellitus at least in children, but high plasma triglycerides secondary to diabetes or not is associated with higher FNp concentrations which may have implications on atherogenesis. Plasma cholesterol, apolipoproteins AI, B100 and lp(a) are not significant determinants of FNp in type I diabetic children.