Hepatitis C infection is important global health problem with wide spectrum of health, social and economic consequences. The goal of this research was to estimate prevalence of hepatitis C virus infection in risk groups, and to determine association hepatitis C virus (HCV) infection and risk factors. Research included 4627 subjects divided in two groups. Test group included 2627 subjects divided in 4 subgroups with risk for HCV infection: those who received blood transfusion without screening on HCV (it was introduced in 1995) (700); intravenous drug users (60); patients on hemodialysis (168) and health care workers (1699). Control group included 2000 healthy volunteer blood donors. In all subjects anti-HCV antibodies were tested with third generation ELISA test. Positive serum samples were tested for presence of HCVRNA, using reaction of reverse transcription and polymerase chain reaction. In all anti-HCV positive subjects further epidemiological and clinical workup was performed. Prevalence of HCV infection in risk groups was: 4.6% in subjects who have received blood transfusions without HCV blood screening, 35% in intravenous drug users, 58.9% in patients on chronic dialysis, and 0.4% in health care workers. In control group prevalence was low (0.2%). In the group of 158 anti-HCV positive subjects, 73.4% had HCVRNA. The largest number of subjects with HCV infection was in the age group of 30-49 years (45.8%). This study showed that multiple blood transfusions before introducing the blood screening for HCV, longer duration of intravenous drug abuse, longer duration of hemodialysis treatment, larger number of accidental injuries in health care workers are independent and statistically significant risk factors for those groups examined. Results of this study confirm that general screening for HCV infection is recommended in risk groups for HCV infection in order to identify to prevent and to treat it.