Resistance rates to selected antibiotics of Gram-negative bacteria isolated from intensive care units (ICU) of 16 Turkish hospitals during 1998 were evaluated and compared to data from the previous 3 years. Antibiotic susceptibilities to imipenem, ceftazidime, ceftazidime-clavulanate, cefoperazone-sulbactam, ceftriaxone, cefepime, cefodizime, cefuroxime, piperacillin-tazobactam, ticarcillin-clavulanate, gentamicin, amikacin and ciprofloxacin were determined by Etest, A total of 1,404 isolates from 1,060 patients were collected, mainly from urinary and respiratory tracts. As in the previous 3 years, Pseudomonas spp, was the most frequently isolated Gram-negative species (29.7%), followed by Escherichia coli, Acinetobacter and Klebsiella spp, Imipenem was the most active in vitro agent (73.4% susceptible), followed by ciprofloxacin (60.6%), cefoperazone-sulbactam (58.7%), cefepime (56.7%), piperacillin-tazobactam (55.0%) and amikacin (54.7%). In 1996, a decline in susceptibility rates of all antibiotics was evident. With the exception of imipenem, resistance to which remained stable, rates somewhat increased in 1997, In 1998, susceptibility to imipenem and cefepime remained stable, amikacin resistance tended to increase and susceptibility rates to other antibacterials showed a favorable increase. These results may in part be due to the implementation of a surveillance program and increased understanding of the magnitude of the resistance problem.