Injection of hemoglobin-containing complex of serum proteins isolated from animals with Ehrlich carcinoma led to regression of intraperitoneally and intramuscularly transplanted Ehrlich carcinoma in male C57Bl/6 mice. The hemoglobin-containing complex of serum proteins disturbed cycle distribution of Ehrlich carcinoma cells and caused apoptosis of about 34.3% tumor cells. Addition of hemoglobin-containing serum protein complex into Ehrlich carcinoma incubation medium did not lead to the death of tumor cells and even slightly increased their proliferation.