The development of specific medical forms for fighting against the tumor disease (cancer) of people and animals has the extremely important value. The preparation «ZG-2011» («Leucozav») was invented in 2000-2006 by research associates of SSI “State center of innovative biotechnologies” that forms in inoculated animals the specific anti-viral immunity that protects cattle from being infected by the leucosis causative agent. Analogues of this preparation in Ukraine are absent. The main aim of the study is the determination of “Leucozav” influence on morphologic parameters of blood (leukocyte profile) of clinically healthy cows and ones, infected by leucosis.The object of the study was blood of cattle (milk herd), considered as unfavorable as to leucosis.Blood samples were studied before administering “Leucozav” and after that. Serological and immunological research methods were used.At the experiment it was studied, that «Leucozav» administration to infected animals normalizes leukocytes number and the ratio of their separate forms in blood of cows. In blood samples, taken of healthy cows, the preparation administration doesn’t influence the leukocyte profile.This experiment gives grounds to recommend the newly created preparation«Leucozav» to cows with leucosis, because it normalizes the number of leukocytes and their ration in separate forms in blood of RID-positive cows that react positively at the immune diffusion reaction in the agar gel at the study of leucosis of cattle.