A ectromelia-like disease in th colony of wistar strain rats was studied. The clinic signs,dermal lesions of the disease rats are similar to mouse pox. The morbidity of this disease is 44.5%. The fatality^ rate is 11.3%. Type A inclusion bodies were observed in dermal dermis and hypodermis tissues of disease rats as well as in the epithelial cells of the chick embryo chori-oallantoic membrane ( C.E. C.M ) with the pox pock induced by inoculation of the tissue suspention from a disease rat. The disease was reproduced artificially in mice and rats which are good health following inoculation with livers,spleens and dermal necrosis tissue suspension of the disease rats.And the virus was isolated and a cytopathogenic effect was observed in IBRS2 cell line. The disease was also reproduced by the culture suspention of IBRS2 cells with the virus or the suspention of homogenized tissue of C.E. C.M which was inoculated with the suspention of the tissues of the disease rats. It is demonstrated by means of the agglutination test coordinated by SPA that the antigenicity of the virue isolated is the same as that of the pathogenic agent. Under the electron microscope viral particles with envelope were morphologically similar to poxvirus and 250-350 nm in diameter.