Objective. Despite the importance of blood flow regulation (BFR) in cerebral vessels, in particular, during organism development, there is no studies in children in the first weeks of life. We studied biochemical autoregulation of blood flow in infants born at 24-25 weeks of gestation. Material and methods. Eighteen infants with body mass 763±138 g were included in the study. Results. There was a high frequency of intraventricular hemorrhages (77%, 14 infants), including those of III stage (50%) with ventriculomegalia (9 infants). Cystic periventricular leukomalacia developed in 50% (9 infants). Retinopathy of premature children with localization in the posterior pole of eyeball developed in 100% of cases. Results of capillary blood gas analysis (pO2, pCO2 and parameters of resistance index of anterior cerebral artery measured using Doppler ultrasound) were studied from 25 to 30 weeks of gestation. In the first weeks of life, spastic character of blood flow in the anterior cerebral artery against the background of hypoxemia and relative hypocapnia was found. No data on the hyperoxic autoregulation of blood flow was obtained. The hypercapnic mechanism of autoregulation had developed earlier and emerged from the 28th week of gestation. Conclusion. The dramatic increase in hypercapnia leads to the blood inflow to tissues and finally to the early development of retinopathy, periventricular leukomalacia and intraventricular hemorrhages.