The revised case definitions established by the Robert Koch Institute will become effective on 1 January 2007. The case definitions provide criteria for the reporting of mandatory notifiable infectious diseases according to the German infectious disease control act. The new case definitions take into account recent developments in laboratory methods. Furthermore in the new edition the criteria were updated and clarified if necessary. For each case definition a paragraph 'reference definition' is introduced and explained. If applicable additional information (e.g., vaccination history) to be reported was added. In this article, the major changes of the revised case definitions are described.