Persistence of viral post-transfusion hepatitis together with epidemiological data led to identify 3 forms of clinical non A non B hepatitis: enteric, post-transfusional and sporadic hepatitis. Two groups of viruses are responsible for this pathology; they are designated as HEV (Hepatitis E Virus) and HCV (Hepatitis C Virus). HEV described by D. Bradley is a 27 to 34 nm. non enveloped particle containing a single strand RNA and belonging to the calicivividae family. HCV described by M. Houghton is a 50 to 60 nm. enveloped virus containing a 10,000 nucleotide long single strand RNA who belongs to the Flaviviridae family. The serological diagnosis is based on the detection of antibodies against the C100-3 antigen, a 363 amino acid recombinant protein produced in yeasts. Reactive samples are to be confirmed for antibodies specificity by using a neutralization assay in the presence of the same antigenic material. Alternatively, it is also possible to identify some sequences of viral genome in the serum, after amplification by the technic of Polymerase Chain Reaction (PCR).