Significant differences were found between four strains of goatpox virus isolated from goats in Egypt, Iraq, Iran and the U.S.S.R., namely in their growth behaviour in embryonated eggs, ceiling temperature, plaque characteristics in cell culture, heat resistance and in the degree of inhibition of their replication by actinomycin D and bromodeoxyuridine. All the strains studied had morphologically similar virions and induced type A V- inclusions. They were uncapable to produce haemagglutinins in infected cell cultures. Antigenically, the strains were indistinguishable.