Antigenic relationships among sheep pox, goat pox and contagious pustular dermatitis (CPD) viruses were determined by serological techniques using soluble antigens partially purified by DEAE-cellulose chromatography. Homologous antigen-antibody reactions were characterized by the presence of 7 precipitation lines with sheep pox and of 5 ones each with goat pox and CPD viruses. The nature of cross-reactions of sheep pox, goat pox and CPD virus soluble antigens with corresponding sera suggested that sheep pox virus shared 3 soluble antigenic components with goat pox and either 3 or 4 ones with CPD virus. Goat pox virus shared either 2 or 3 soluble antigenic components with CPD virus. Cross-neutralization tests revealed an one-way cross of goat pox virus with sheep pox and CPD viruses, respectively. The results showed that the 3 viruses in question share common soluble antigenic components.