The authors report the results of studies on antitumor, immunostimulating and interieron-inducing properties of diethylamine fluorene derivative--tiloron, synthesized at Odessa laboratories of IGIC of the Ukrainian SSR Academy of Sciences by the originally elaborated method. It was found that tiloron does not suppress leucopoiesis, stimulates a number of protective reactions of the organism, including the factors of humoral and cell immunity, especially manifested under immunosuppression. Tiloron is shown to possess the definite antitumor activity being retained in peroral administration of the drug. Tiloron used together with cytostatic agents results in enhanced suppression of experimental tumors growth. Antitumor and immunostimulating action of tiloron on the experimental patterns under study is believed by the authors to be somewhat related with its interieron-inducing ability.