Acinetobacter baumannii is a well known but relatively uncommon cause of health-care--associated infections. Because the organism has developed substantial antimicrobial resistance, treatment of infections attributed to A. baumannii has become increasingly difficult This report describes an increasing number of A. baumannii bloodstream infections in patients at military medical facilities in which service members injured in the Iraq/Kuwait region during Operation Iraqi Freedom (OIF) and in Afghanistan during Operation Enduring Freedom (OEF) were treated. The number of these infections and their resistance to multiple antimicrobial agents underscore 1) the importance of infection control during treatment in combat and health-care settings and 2) the need to develop new antimicrobial drugs to treat these infections.