Abstract: Objective To investigate the proliferative capacity and collagen secretion of transplanted human fibroblasts. Method The solution containing human fibroblasts(2×107/ml) was prepared and 1ml was injected into the dermis of BALB/CNU nude mice. Animals were killed respectively at the end of the 1st,2nd and 3rd month after injection. The dermis in the injected area was taken out and stained with HE. Immunohistochemical staining for type I and type III collagen was performed at the same time. Results Mitosis was observed at the end of the 1st,2nd and 3rd month. The concentration of type I and type III collagen in the extra cellular matrix increased with the passing of time. Conclusion Transplanted human fibroblasts can proliferate automatically in the dermis of nude mice and manufacture the type I and type III collagen in situ. Long period of survival and secretion will make it possible for fibroblasts to become promising option to correct minimal tissue defects.