Epidemiological data from recent years confirm the increasing problem of antimicrobial resistance not only for healthcare-associated, gram-positive pathogens but also for gram-negative bacteria. In particular, the progressive increase in resistance to third generation cephalosporins and carbapenems in Enterobacteriaceae is of great concern. With its contribution to infectious morbidity, mortality and financial costs to healthcare systems worldwide, multidrug-resistant pathogens emerge more and more as a public health issue of substantial socioeconomic importance. The Commission for Hospital Hygiene and Infection Prevention (KRINKO) at the Robert Koch Institute (RKI) decided to formulate novel definitions for multidrug-resistance in order to develop hygiene measures for infections and colonization with multidrug-resistant gram-negative bacilli.