We studied subpopulation structure of rat cord blood and its effects on regeneration of the bone tissue. In cord blood leukocytes, cell fractions with phenotypes CD45+/CD90-, CD45-/CD90+, CD34+/CD45+ were determined. The cells adhered to plastic during culturing and had a fibroblast-like morphology. Transplantation of rat cord blood cells into modeled femoral bone defects stimulated regeneration of the bone tissue and led to recovery of its anatomical integrity, which was confirmed by X-ray examination and histological analysis. No complete recovery of the bone structure was observed in controls (without cell implantation).