The recent discovery of an antigenic component of the causative agent of Non-A, Non-B hepatitis, has led to the characterization of this virus--Hepatitis C Virus (HCV)--and to the identification of an antibody present in infected subjects (anti-HCV) detected by means of the C-100 antigen derived from a nonstructural region of the viral genome. Using a commercial Kit (Ortho Diagnostic Inc.), the incidence of anti-HCV antibody was studied in the Military Hospital "Dr. Carlos Arvelo" of Caracas, Venezuela with the following results: Health personnel (doctors, nurses, laboratory staff): 102 persons studied, 2 positives (1.96%); 16 patients in chronic hemodialysis: 6 positives (33%); 20 subjects with antibodies against HIV virus, confirmed by Western Blot: 7 positives (35.4%). Of 10 patients with Surface Antigen negative Chronic Hepatitis, 7 (70%) positive for anti-HCV, of 25 patients with cirrhosis: 12 positive (48%), 2 patients with hepatocarcinoma 1 positive (50%). There was also a high incidence of total anti-core antibodies in the patients studied. The results suggest that the hepatitis C virus could be playing an important role as a causative factor of liver diseases in our Country.