Aim — to evaluate the effect of exogenous melatonin on the blood-retinal barrier and oxidative status of the vitreous in rats with oxygen-induced retinopathy (OIR) and analyze its prospects in the treatment and prevention of retinopathy of prematurity (ROP). Material and methods. The study was performed on 48 Wistar rat pups (96 eyes) divided into 4 groups 12 animals each: OIR group, melatonin group and two control groups. In order to induce retinopathy, rat pups and does were placed in an incubator for 14 days after birth. Oxygen concentration in the incubator changed from 60 to 15% every 12 hours. The controls for this experiment were rats that grew under normoxic conditions (21%). The two other groups of rats were injected with 30 ml intraperitoneal melatonin (Sigma-Aldrich) in sterile 0.05 M phosphate buffer (pH 7.4) at a dose of 10 mg/kg for 14 days starting on day 1. The pups were killed on days 7 (n=16), 14 (n=16), and 18 (n=16). Binocular enucleation was performed in all cases. The total protein level and antioxidative activity (AOA) were then measured in vitreous samples. Results. Oxygen-induced retinopathy had two phases and was accompanied by a sharp increase in the vitreal AOA and total protein. After intraperitoneal melatonin injections made during the period of early OIR-associated vascular changes, the said parameters were decreased down to near-control values at any times during the follow-up period. Conclusion. Exogenous melatonin, due to its strong antiangiogenic and antioxidant activity, helps stabilize the blood-retinal barrier in OIR.