Prior to the process of viral inactivation in the 1980s most haemophilic patients were infected with hepatitis C virus, currently one of the disease's main causes. The prevalence of infection by hepatitis C virus in haemophilic patients enrolled in the Hemocenter of the Regional University Hospital maintained by the State University of Maringá is evaluated from social and epidemiologic data and from serum and molecular tests. Possible association between haemophilia's type and severity, type of treatment, data of start of treatment and hepatic enzyme rates of Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST) was verified. Sixty-nine haemophilic patients, 82.6% with haemophilia A and 17.4% with haemophilia B, in the 1 - 67 years age bracket, average age 22 years, were investigated. Whereas anti-HCV was investigated with third generation immunoenzymatic test and confirmed by HCV-RNA, LiPA technique determined genotypes. HCV-prevalence infection reached 37.7% and 21.7% respectively when antibody anti-HCV and HCV-RNA detection and associated significantly (p<0.05) with type of treatment, date of start of treatment and ALT and AST hepatic enzyme rates are taken into account. HCV genotype 1 predominated (53.3%) followed by genotype 3 (40.0%) and genotype 2 (6.7%). HCV predominance is high in haemophilic patients although infection has not been reported in patients under the age of 17.