The antibody to polymerized human albumin (anti-pHSA) was studied in normal subjects and in the course of infection from hepatitis A virus, hepatitis B virus, and hepatitis non-A, non-B virus. Results show that anti-pHSA antibody was never found in normal subjects, but it appeared during virus liver pathologies. The behavior of anti-pHSA differs in acute type A hepatitis that does not change to chronic form and in those forms which tend to become chronic (B and nonA, nonB). In the type-A infection anti-pHSA disappears after the acute phase; in the other two forms it persists all along as the infection develops. Specifically in non-A, non-B infection only the IgM type anti-pHSA is produced.