An oncofetal protein, human alpha-fetoprotein, was selected as a vector molecule for targeted delivery of antitumor substances. Conjugates of alpha-fetoprotein with doxorubicin, daunomycin, calichemicin, carboxyphosphamide, bleomycetin, chlorbutin, cis-platinum, methotrexate were synthesized. All conjugates displayed a highly selective antitumor cytotoxic activity towards human cell cultures. The optimal alpha-fetoprotein:cytotoxic compound ratio was shown to be 1:3 - 1:5. The results obtained serve as a basis for creating antitumor preparations of a new generation, which are highly selective to tumor cells owing to receptor-mediated endocytosis.