To study the expression of c-Fos and Rb in radiation-induced rat skin ulcers. We set up an animal model of radiation skin ulcer with 140 rats which were locally irradiated with 35~55Gy γ rays, and the pathological changes were observed for 1 year. Immunohistochemical studies were performed in 72 rat radiation skin ulcer tissues, and c-Fos, Rb protein polyclonal antibodies were used. The results showed that the positive rate for overexpression of c-Fos was 45.8%, and for that of Rb was 63.9%. The positive position was mainly in the nucleus of activated squamous epithelial cells and in some fibroblasts, endotheliocytes of the arterioles in mesenchyme. It is suggested that the overexpression of c-Fos and Rb proteins might be related to canceration and poor healing in radiation skin ulcers.