To evaluate the rate of HCV and HDV infections in Yugoslavia, a statistically appropriate number of random blood donors and members of selected population groups with varying risks of exposure to HCV and HDV, respectively, were tested for the presence of anti-HCV and anti-HDV antibodies, using ELISA test kits produced by Abbott Laboratories. The results demonstrate that: (a) the prevalence of anti-HCV in random blood donors was 0.71%; (b) 43.48% of hemodialysis patients were anti-HCV positive; and (c) anti-HDV was detected in 1.35% of HBsAg-positive blood donors and in 13.88% of the intravenous drug abusers tested. Taken together, these results confirm the presence of HCV and HDV infections in the Yugoslavian population.