At present 10 to 30 per cent of the microbial strains from cancer patients are problem ones: oxacillin resistant strains of Staphylococcus aureus, coagulase negative strains of Staphylococcus spp., aminoglycoside resistant strains of Escherichia coli, 3rd generation cephalosporin resistant strains of Klebsiella spp. and fungi of Candida which requires development of more rational approaches to antibacterial chemotherapy and prophylaxis of infectious complications. The infectious processes in the cancer patients proved to be highly polyetiological. Therefore, the study is significant for epidemiologic and therapeutic measures. Such an analysis in oncological clinic should be regular.