As the incidence of liver disease in hepatitis-associated antigen (HAA) carriers has not been defined and it has been postulated that continuing liver disease is associated with incompetence of the cell-mediated immune system, a prospective study was undertaken to examine both these points.An increased incidence of HAA carriers was found in a prison population (1.3%). Eighteen of these subjects gave informed consent to further study with liver function tests, liver biopsy, and testing of cell-mediated immunity with dinitrochlorobenzene (DNCB) skin sensitization. Liver function tests were normal in 10 subjects, mildly abnormal in six (SGPT < 100 IU/litre), and abnormal in two. Serum proteins were normal in all. Liver biopsy showed that five subjects had chronic aggressive hepatitis, three of whom had normal liver function tests. Eight subjects had persistent hepatitis, three with normal liver function tests. The remainder had acute hepatitis (1), evidence of residual hepatitis (1), or non-specific changes (2). Only one subject had normal histology. Drug addicts, who comprised 56% of the group, had more severe liver disease then those who were not addicts. The hypothesis that persisting liver disease is associated with impaired cell-mediated immunity was not confirmed in that nine of the 12 subjects with persistent or chronic aggressive hepatitis had a positive response to dinitrochlorobenzene skin sensitization, thus implying normal cell-mediated immunity. The findings of this study suggest that in the presence of continuing antigenaemia liver biopsy is mandatory in order to disclose treatable liver disease.