Prcscnted is a review of basic information on the causative agents, epidemiology, and therapy of viral hepatitis B and type C. Speciál attention is devoted to active and passive immunizalion, including posl-exposu-rc intervention. The major routě of transmission in virus hepatitis B is presently heterosexual intercourse. That is followed by intravenous drug abuse, homosexuál activities and risky techniques of sexual intercourse. A significant routě is also vertical transmission from mother to newborn. The virus of type B hepatitis belongs to the most complicated of DNA viruses, in the course of its replication cycle the originál DNA being transcribed into RNA and then according to that template new viral DNA is formed. Věry complicated is also the interacti-on between the virus and the immune systém of the host organism. That interaction results in a varying cli-nical course on the one hand, and a number of so-called stages of infection on the other. In most cases those stages can be differentiated with the aid of serological diagnostic methods. However, for a correct interpretation of their results it is necessary to know the significance and function of each antigen and cor-responding antibody. The significance of those proteins and the separate serological findings are explained in detail. Presently, specific antiviral therapy is indicated only in chronic infections with hepatitis B virus in the stage of active virus replication. There are two basic therapeutic options: interferon alpha and the virostatic lamivudin. In the čase of infection with type B hepatitis virus there is available passive as well as active immunization, both being deseribed in detail, including indications and vaccination procedures. The virus of hepatitis C has been identified in 1989. The major routě of transmission up to the year 1992 were products derived from blood; after 1992 when blood transfusion units began to use detection sets for demonstrating anti-HCV antibodies, the incidence of post-transfusion type C hepatitis fell almost to zero. Presently, the major routě of transmission is intravenous drug abuse, however, no small share is played by health care. The basic serological marker of HCV infection are anti-HCV antibodies. Those antibodies are an indicator of contact with the virus, not necessarily meaning the subject has experienced an infection. Rat-her, Ihe contrary is Ihe čase. In as hepatitis C virus infeclion passes inlo the chronic slage in up lo 85% of cases, anti-HCV activity mostly signifies active infection with type C hepatitis virus. For the demonstrati-on of active infection there is necessary a positive demonstration of viral nucleic arid in the sérum of the person investigated. The standard treatment of chronic infection with hepatitis C virus is a combination of pegylated interferon alpha and ribavirin, laeding to permanent eiimination of the virus in 60% of cascs. Thc-re is no available specific pre-exposure oř post-exposure prophylaxis of hepatitis C virus infeclion. The only prevention of transmission of the disease is the avoiding of all risk factors of transmission, námely whcn affording health care.

        Key words: hepatitis B virus - hepatitis C virus - lamivudin - interferon - pegylated interťeron - vaccina-tion.