According to different authors, the emergence of enterococci with high-level aminoglycoside-resistance reaches values of 4.5-55%. The objective of this work is to determine the frequency of these strains in our hospital. We have studied 274 strains of enterococci isolated in our centre, of which 235 were E. faecalis and 39 E. faecium. Strains were obtained from haemocultures (75), urine cultures (100) and other samples (99). The detection of high-level resistance was performed on Mueller-Hinton agar, containing concentrations of 2,000 mg/l of streptomycin, kanamycin, gentamicin, tobramycin or amikacin. MICs and MBCs were determined for several antibiotics by microdilution. We detected the presence of high-level resistance to streptomycin, kanamycin, gentamicin, tobramycin and amikacin in 29.1%, 52.9%, 31.0%, 26.6%, and 1.8% respectively. The more active antibiotics against the strains with high-level resistance to gentamicin were: mezlocillin (MIC90 = 1.0 mg/l), piperacillin and vancomycin (MIC90 = 2.0 mg/l), and ampicillin and imipenem (MIC90 = 4.0 mg/l).