The morphological criteria for diagnosing chronic hepatitis are discussed and criticised. A classification closer to clinical reality than that of De Groote et al 1968 is then proposed. Personal experience in differential laboratory diagnosis between the various forms of chronic hepatitis by means of comparative evaluation of an enzymogram and the measurement of certain proteins in the serum is then reported. Case examples are given to emphasise the possibilities of the immunological approach to the problem of active chronic hepatitis. Finally, the cardinal points of therapy are reviewed.