Case definitions ensure standardised criteria for the surveillance of infectious diseases in Germany. Since its last revision in 2007, an update of the complete case definition edition became necessary due to new scientific insights, changes in legislature, terminology and classification systems. At the same time, the case definition should be further standardised and work at local public health authorities should be simplified. The department for infectious disease epidemiology at the Robert Koch Institute (RKI) coordinated the revision of the case definitions. During several feedback sessions, internal RKI experts and external experts from different levels of the German public health system, as well as from medical associations and laboratories, were involved in the revision process. The new edition and an annotated version are published on the RKI website (www.rki.de/falldefinitionen). The new case definitions will become effective on 1st January 2015. The most important changes are summarised in this article.