230 clinical isolates of Acinetobacter species were characterized according to genospecies (new taxonomy), relative frequency of isolation, distribution in clinical samples and resistance pattern. A.baumannii was more frequently found than any other species (42%), followed by A.lwoffii (28%), although only 60% of the former "A.lwoffi" corresponds to the new A.lwoffii. The other 40%, formerly A.lwoffi, were shared by A.junii and A.haemolyticus. Concerning habitat and resistance pattern, remarkable differences between the new biotypes were found. A.baumannii and A.lwoffii were isolated mainly from swabs. A.calcoaceticus was most frequently cultivated from samples of the upper respiratory tract, and from blood cultures preferably A.baumannii and, more rarely, A.lwoffii and A.haemolyticus were isolated. A.baumannii showed multidrug resistance against beta-lactam antibiotics, most of the tested penicillins and cephalosporins. The two most susceptible species in our study were A.junii and A.lwoffii. Resistance to imipenem, aminoglycosides and quinolones was rare with all strains.