Acinetobacter emerged as a significant nosocomial pathogen during the late 1970s, probably as a consequence, at least in part, of increasing use of broad-spectrum antibiotics in hospitals. Most clinically significant isolates belong to the species Acinetobacter baumannii or its close relatives, with many infections concentrated in intensive care, burns or high dependency units treating severely ill or debilitated patients. Large outbreaks can occur in such units, involving the infection or colonisation of numerous patients by specific epidemic strains of A. baumannii. Recently, a particular problem has concerned cross-infection of injured military patients repatriated from combat regions of the world (e.g. Iraq and Afghanistan). Carbapenems have previously been the treatment of choice for infected patients, but increasing reports worldwide now describe A. baumannii isolates resistant to all conventional antimicrobial regimens. Data to support therapeutic use of the limited number of new antimicrobial agents (e.g. tigecycline) with in-vitro activity against these pathogens are still very limited. Detailed advice concerning prevention and control of outbreaks caused by multidrug-resistant strains of acinetobacter is available from the UK Health Protection Agency. In addition to antibiotic prescribing policies and audit, these measures focus on reinforcing standard infection control procedures and precautions, with particular attention to thorough cleaning of patient areas to take account of the long-term survival of acinetobacter after drying and inadequate disinfection. Despite these measures, the problem continues to escalate, with many hospitals worldwide now reporting outbreaks caused by multidrug-resistant strains of acinetobacter.