Nitric oxide (NO) is an endogenous vasodilator involved in inflammatory and autoimmune response, and in the pathophysiology of diabetic vascular disease. Endothelium-derived NO is formed from L-arginine by endothelial NO synthase (eNOS), and earlier studies have provided evidence for altered NO metabolism and impaired endothelial function in diabetes, probably due to polymorphisms in eNOS gene. In the present study we investigated the association of the eNOS gene intron 4 a/b VNTR polymorphism with diabetic microangiopathy in 61 young individuals with type 1 diabetes (T1D), 35 male and 26 female, aged 5.0-29.1 (mean 15.6) years, and followed up for 3.24-11.4 (mean 7.44) years. Ten patients (16.4%) had developed microalbuminuria, three hypertension and two retinopathy. Wild-type b/b homozygosity for eNOS gene intron 4 VNTR was found in 37 (60.7%) and a/b polymorphism in 24 (39.3%). No significant relationship was demonstrated between eNOS gene intron 4 polymorphisms and microalbuminuria, hypertension or retinopathy in these young individuals. Our findings suggest that a/b polymorphism of the intron 4 eNOS gene is not associated with early onset diabetic microangiopathy.