Two hundred patients with different liver diseases were observed during a period of 6-8 years. The diagnosis at the first hospitalization was based on morphological criteria (and, in some cases, additional clinical information). In 162 of the cases an initial 'specific' diagnosis could be made. By the time of the follow-up study the diagnosis was confirmed in 73% of them. In 22 of 38 patients who were initially unclassifiable, the diagnosis was made definite by the follow-up study. Eighty-five patients were hospitalized for re-examination 6-8 years after the initial study. Several of the liver diseases initially had quite typical patterns of clinical chemical data. Allocation by discriminant analysis was therefore in good agreement with the morphological classification. The follow-up study showed that several patients with initially atypical patterns of clinical chemical results had their diagnosis changed. In 35 patients with the final diagnosis of chronic active hepatitis (CAH) or primary biliary cirrhosis (PBC), laboratory data from the last hospitalization were used for discriminant analysis with teaching data from the initial study. Ninety-seven per cent were correctly allocated, and we conclude that these patients retain recognizable patterns of laboratory results for several years, even when given immunosuppressive treatment. The potential clinical usefulness of discriminant analysis of laboratory data for differential diagnosis was evaluated by a prospective study of 65 patients with the morphological diagnosis of CAH or PBC. Correspondence with the morphological classification system was found in almost 90% of the cases.