A retrospective survey was conducted of the characteristics of acinetobacter infections in Hong Kong — seasonal and geographic distributions, frequency of isolation from various body sites, antimicrobial susceptibility and molecular epidemiology. Most (80%) isolates of Acinetobacter spp. belonged to DNA groups 2 (A. baumannii) or 13, as defined by growth at 44°C. An increased isolation rate in summer was related to higher ambient temperatures. The notion that acinetobacters are opportunist nosocomial pathogens was supported by the body site- and ward-specific distributions, which were similar to those of Pseudomonas aeruginosa and in marked contrast to those of coagulase-negative staphylococci and Escherichia coli. Typing of Acinetobacter isolates by arbitrary-primed polymerase chain reaction revealed extensive genotypic polymorphism, suggesting that numerous unrelated strains were circulating between patients. In view of the association with a high incidence of polymicrobial bacteraemia and multiresistance to antibiotics, a careful selection of appropriate antibiotics in combination is necessary for empirical therapy of infections caused by Acinetobacter spp.