Gram-negative non-fermentative aerobic bacilli are becoming increasingly more involved in nosocomial infections. It has generally been recognised that the members of the Acinetobacter genus are among the most common agents responsible for severe hospital infections; their clinical importance has increased due to the development of antibacterial resistance mechanisms by these organisms. Over the last two decades the antibacterial armamentarium has progressed significantly and newer broad spectrum antibiotics have been used during therapy of hospital infections due to drug-resistant Acinetobacter spp. Despite various mechanisms of resistance to beta-lactams, aminoglycosides, fluoroquinolones developed by these organisms, the control of Acinetobacter infections can be effected by the use of several antibiotic combinations in 'conventional' antibiotic therapy. Recent surveys have pointed out the importance of using combinations of 2-amino-5-thiazolyl cephalosporins, or imipenem with aminoglycosides, or alpha-carboxy- penicillins (ticarcillin) combined with beta-lactamase inhibitors. Amongst the latter drugs, the place of sulbactam should be redefined thanks to its intrinsic activity against the Acinetobacter species, associated with its inhibitory power against beta-lactamases. The fluoroquinolones were initially very active against Acinetobacter infections, but resistance to this major class of drugs has occurred very rapidly. However, newer compounds of this class with increased anti-Acinetobacter activities can be used in combinations with beta-lactams or aminoglycosides. The potential role of rifampicin is still underestimated for the treatment of Acinetobacter infections despite promising in vitro activity. Novel derivatives of cephalosporins, carbapenems, fluoroquinolones, or completely new antibiotic classes, of which several investigational drugs seem promising, may constitute the future of antibiotic therapy and hence the treatment of Acinetobacter infections.