Two camelpoxvirus (CPV) strains isolated from camels with generalized skin-disease were serially passaged on Vero cells. Various phenotypic properties were investigated in vitro and in vivo and compared with those of the corresponding wildtype strains. In many aspects no differences were observed. However, in a mouse model both passaged strains proved to be highly attenuated. In addition, both strains failed to replicate in a cell line derived from camel skin cells. Comparison of physical maps established for enzymes HindIII and Xhol revealed deletions accounting for a total of 22 kbp in one attenuated strain. In the second strain only minor alterations were noted.