The prevalence of genetic variants (subtypes) of hepatitis C virus (HCV) among HIV-infected and noninfected intravenous drug users (IDU) in Russia is studied. HIV and HCV infections spread in the population of IDUs in Russia irrespective of each other. HCV subtypes 1b, 2a, and 3a (35.2, 18.3, and 29.6%, respectively) are the most prevalent in Russia. The profile of HCV subtype distribution in Russia differs from that in Europe; a "domestic" origin of HCV infection among IDUs is suggested. The authors conclude that identification of HCV subtype should be included in the protocol of examination of HIV-infected patients.