Background and Aims: Thickening of basement membrane in capillaries and small vessels is a well-known finding and important in the progression of diabetic microangiopathy. Patients with diabetes mellitus and arterial hypertension are at higher risk of vascular disease. Material and methods: To monitor the metabolism of the basement membrane protein collagen type IV (CIV) in type 2 diabetes mellitus (T2DM), serum levels of antibodies to CIV (ACIV) IgG, IgM and IgA were measured using an ELISA method in 93 patients with type 2 diabetes mellitus and arterial hypertension (AH) (mean age 61,4±11,3 years, diabetes duration 9,88±3,12 years; hypertension duration 9,28±4,98). These values were compared to serum antibodies to CIV in 42 age and sex matched controls. Diabetics were divided in two groups according to presence- Group 1 (n=67) or absence- Group 2 (n=26) of microangiopathy. Results: Patients with T2DM and AH showed statistically significant higher levels of ACIV IgG in comparison to healthy controls (0.30±0.12 vs. 0.21±0.08) (p=0.0001). Group 1 showed significantly hihger levels of ACIV IgG than Group 2 (0.32±0.13vs. 0.24±0.08) (p=0.009) and healthy controls (0.32±0.13vs. 0.21±0.08) (p=0.0001). ACIV IgG are statistically significant higher in diabetics with retinopathy than this without (0.33±0.10 vs. 0.26±0.13) (р=0.04). ACIV IgG correlates with diabetes duration (r=0.49); (p=0.0004), retinopathy (r=0.20); (p=0.05) and BMI (r=-0.24); (p=0.05). Serum ACIV IgM and IgA levels in patients with T2DM and AH were lower than these in controls, but the differences are not statistically significant.Conclusion: Our study showed a relationship between elevation of serum levels of ACIV IgG in diabetics and development of microangiopathy.