The regeneration of osseous tissues after implantation of rat osteoblast-like cells cultivated in vitro was investigated. A cell line of rat osteoblast-like cells originating from explants of four inbred rats (Lewis) was established. The osteoblast-like cells were cultivated in vitro and re-implanted after 3 passages in cell culture into artificial femur defects of the same inbred Lewis rats. The cultivated osteoblast-like cells were embedded in bovine bone gelatine and implanted together with hydroxylapatite granulate (12 animals), pyrolized calf bone (12 animals) or without any additional material (12 animals). These bone replacement materials were used as a carrier for the osteoblast-like cells. After 10, 20, 40 and 80 days animals were killed and the treated femora were taken for histological examination and determination of bone growth rate. It was demonstrated that the cultivated osteoblast-like cells in this experiment had no measurable effect on quantitative bone growth, but caused a significant difference in the histological bone regeneration pattern.