We have evaluated the intrafamilial transmission of hepatitis C virus (HCV) by studying 1) the 107 household contacts of 43 patients with chronic HCV liver disease, 2) the household contacts of 30 anti-HCV-positive donors without liver disease, and 3) 3108 blood donors. We also studied the possible manner of the intrafamilial transmission. The prevalence of anti-HCV positivity in the families of index patients was significantly higher than in donors (14.9% as against to 1.7%). All the family members of the anti-HCV-positive donors were anti-HCV negative. We conclude that the person-to-person transmission of HCV is possible and most probable in contacts of anti-HCV-positive patients with liver disease.