Hepatitis C genotype 4 (HCV-4) is considered to be rare outside northern Africa and southern Europe.To describe the epidemiological characteristics of patients infected with HCV-4 in Poland.The study group included 290 patients with HCV-related chronic liver disease and intravenous drug users with HCV infection recruited in years 2002-2006 in Podlaskie region, north-eastern Poland. In all cases, HCV infection was confirmed by HCV-RNA detection by qualitative nested RT-PCR. HCV genotype was determined by 5'UTR sequencing and comparison with known genotype-specific sequences.HCV 4 was found in 45 (15.5%) of 290 HCV-infected and HCV RNA-positive individuals. 60% of HCV 4 infections occurred in intravenous drug users; 51% of HCV 4-infected patients were also HIV-positive. Among 119 patients whose source of infection was other than drug use, there were 16 (10.5%) HCV 4 cases. Seven (46%) of 13 HCV 4-positive and HIV-negative patients who received combined antiviral treatment had sustained viral response.HCV 4 exists in eastern Poland, and the infection is frequently related to intravenous drug use and accompanied by HIV infection. HCV 4 also causes a proportion of non-drug-related HCV infections.