Anti-HCV antibody (anti-HCV) tested by means of ELISA was positive in 33 of 38 (86.8%) hemophiliacs examined, and the mean age of the positive patients was lower than that of the negatives. Positivity of anti-HCV was correlated neither to the types of hemophilia, nor to the presence of HBV and/or HIV infection. High GPT levels could be found more frequently in the anti-HCV positive group than in the negative one.In two of our hemophilia A patients, anti-HCV was converted from negative to positive in 1988, during they were administered with the dry heat-treated FVIII concentrated products.As for the human plasma preparation products, anti-HCV was detected as follows: 41/43 lots (95.3%) of immune globulin, 0/65 lots of albumin, 0/2 lots of heat-treated plasma protein fraction, 2/5 lots of FVIII, 0/3 lots of FIX, and 4/4 lots of fibrinogen products.Those findings show the necessity of checking all of the raw human plasma materials for HCV.