The authors describe the isolation and Identification of vaccinia virus fram a cow in farm where human vaccination had been carried out some weeks before. Many of the vaccinated people had developed typical vaccine reaction and had been in close contact with the animais. Two human cases with lesions on hands, have been observed in not vaccinated farm employees; unfortunately the lesions from these human cases were already open and washed with local antisseptics and no attempt to isolate virus could be done. The infection disseminates very rapidly among the animais but no severe symptoms have been observed neither in the animais, nor in the two human cases. The isolated strain has been identified by serological tests (complement fixation and Hl tests) and lesions on the corio-alantoic (fig. 2) of embryonated eggs; the strain could be reisolated from original material kept at minus 20°C. The material collected from the animais was heavily contaminated and it was necessary to use Freon 113 <1 part to 10 of the material suspension) in order to control these contaminants. The possible action of bacterial enzymes against Pox virus in heavily contaminated materiais, is discussed in relation to a recent reference in the literature.