The experiments were performed in mice with transplanted Lewis lung carcinoma. The injections of synthetic peptide vilon at the doses 1 mg/kg significantly increased the survival of mice. So vilon has possessed the oncomodulating action on the transplanted carcinoma. The synchronous injection both of vilon and cyclophosphan at the doses 100 mg/kg decreases the survival of mice. There was also studied in spleen organotypic tissue culture the effect of vilon and cyclophosphan on the development of explants of rats of various age: 1 day and 2 years old. Vilon stimulated apoptosis both in young and old rats, but the inhibitory effect of cyclophosphan was abolished in the presence of vilon in culture media at the dose 5 ng/ml. The results obtained suggested that perspective preparates in the cancer therapy--vilon and cytostatic drugs-, must be used not synchronously.