Susceptibility to ampicillin, penicillin, vancomycin and teicoplanin, high-level resistance to aminoglycosides (gentamicin and streptomycin) and beta-lactamase production were investigated among 264 consecutive clinical enterococcal isolates in Turkey. Disc diffusion test was used to detect resistance to ampicillin, penicillin, vancomycin and teicoplanin. High-level resistance to aminoglycosides was determined both by standard agar screening and by disc diffusion methods. The values of minimum inhibitory concentration (MIC) of each isolate for ampicillin, vancomycin and teicoplanin were determined by the microbroth dilution technique. The isolates were found to consist of Enterococcus faecalis (78%), Enterococcus faecium (9%) and Enterococcus spp. (12%). In all strains, the penicillin and ampicillin resistance ratios were 27% and 26%, respectively. Enterococcus faecalis was more susceptible to penicillin and ampicillin than the other strains. None of the strains were resistant to glycopeptides. High-level aminoglycoside resistance was found in 16% E. faecalis and 88% E. faecium for gentamicin, and 35% and 44%, respectively, for streptomycin. There were no differences between the two methods used to determine the aminoglycoside resistance rates in the enterococcal isolates. No beta-lactamase-producing isolates were detected in either species. In conclusion, to determine the resistance of enterococci to the penicillin group of drugs by the disc diffusion method, both penicillin and ampicillin discs should be evaluated. In serious enterococcal infections, before starting combined therapy, high-level aminoglycoside resistance should be investigated. (c) 2005 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.