Objective: Peripheral arteriolar constriction, increased vascular resistance and structural remodeling are classic features of essential hypertension. Design: To estimate how treatment of patients suffering from HA influences retinal vessels and to evaluate correlation between diameter of arterioles (DA) and venules (DV) and BP parametres. Methods: 49 patients at the age of 57,3 ± 10,3 with mild or moderate HA were qualified for a study (group I). The duration of HA was 5,6 ± 2,4 years. Control group (group II) included 25 clinically healthy people at the age of 51,8 ± 8,6. First group was systematically treated for over a year and for last 3 months they were taken perindopril (10 mg/24 h), amlodipine (5–10 mg /24 h), 20 mg/24 h of simvastatine (43,3%) and 75 mg/24 h of ASA (31,7%). The DA, DV and arteriolar-to-venule ratio (AVR) were estimated, and next clinical parameters of BP were correlated with DA, DV and AVR values. Results: In the first group comparing to control, values of 24-hour SBP was 135 ± 14,8 vs 109 ± 8,9 (p < 0,000), DBP was 79 ± 13,3 vs 64 ± 6,3 (p < 0,000), mean BP 98 ± 13,1 vs 79 ± 6,4 (p < 0,000), HR 72 ± 10,0 vs 65 ± 10,4 per minute. DA was 91,9 ± 8,6 vs 86,8 ± 8,6um (p < 0,0221), DV was 118,5 ± 14,3 vs 121,9 ± 11,6um (p > 0,05) and AVR was 0,78 ± 0,08 vs 0,72 ± 0,09 (p < 0,000). After separating patiens with good control of BP (24-hour BP <125/80, day-time BP <135/85 and night-time BP <120/70) from the first group, it occurred that there were no significant differences in DA and DV between new group and control. We found negative correlation between 24-hour, day and night BP, day and night load of SBP and DBP, and 24-hour variability of SBP and AVR. Conclusions: Good 24-hour blood pressure control in HA patients causes normalization of retinal vascular diameter. Patients with HA have negative correlation between BP parameters, load of HA and 24-hour variability of BP and AVR.