A comparative study of white and yellow venoms of Vipera russelli was carried out by gel filtration and starch gel electrophoresis. It was found that proteolytic activity in the white venom was extremely low, while l-amino acid oxidase and phospholipase A activities were present in lesser amounts. Some substantial differences in the gel filtration elution diagrams of both venoms were observed. In both venoms there was an unidentified fluorescing substance, which probably performs the function of a co-factor to the toxic component. Some data supporting this suggestion are present. By gel filtration and starch gel electrophoresis, the lethal fraction was partially purified. © 1968.