Until today only five pathogens of viral hepatitis have been discovered: hepatitis virus A (HAV), B (HBV), C (HCV), D (HDV) and E (HEV). An update on the state of the art of actually established diagnostic procedures is briefly summarized. Some recent topics and problems are covered more extensively; in the case of HBV the value of HBsAG concentration as a prognostic marker, the finding 'anti-HBc only' the role of HBV mutants, the determination of circulating HBV genomic material, and modalities for HBV vaccination control; in the case of HCV the indications for study of its viral genomic material and the role of HCV subspecies are explained. Finally, first results on HEV prevalence in Switzerland are introduced.