The results of the molecular biological detection of the etiologic agent of hemorrhagic fever in Rostov Province are presented. The role of the causative agents of Astrakhan rickettsial fever, hemorrhagic fever with the renal syndrome, Q fever, leptospirosis and listeriosis has been excluded by means of such immunochemical reactions as the direct and indirect immunofluorescent tests, the solid-phase immunoenzyme assay, the complement fixation test and the agglutination test. The relationship between the cases of hemorrhagic fever in the focus of the outbreak and Crimean-Congo hemorrhagic fever virus has been demonstrated due to the use of the polymerase chain reaction with preliminary reverse transcription.