Acinetobacter, which is Gram-negative non-fermentated bacilli, is isolated from natural environment and human body, including skin and gastrointestional tracts of both healthy persons and immunocompromised patients. Acinetobacter can cause bacterial infections, such as blood stream infections and health care-associated pneumonia. The definition of multi-drug resistant (MDR) of Acinetobacter has not been internationally harmonized, however, it is defined when MICs of imipenem, amikacin and ciprofloxacin are 16 microg/ml, 32 microg/ml and 4 microg/ml or higher, respectively, in Japan. Recently, only a few outbreaks by Acinetobacter have been reported in Japan, while outbreaks by Acinetobacter are more common in Western and Asian countries abroad. We should pay attention and caution on outbreaks by Acinetobacter and spread of drug-resistant Acinetobacter as much as we can.