The aim of this study was to analyse the current prevalence of aminoglycoside resistance in Europe and compare the in vitro activity of amikacin, gentamicin, and tobramycin against 7057 bacterial isolates from 20 university hospitals participating in the European SENTRY Antimicrobial Surveillance Programme. Amikacin exhibited better in vitro activity than tobramycin and gentamicin against most gram-negative bacilli in Europe. The resistance levels were 0.4-3% for amikacin, 2-13.1% for gentamicin, and 2.5-15.3% for tobramycin among different members of the family Enterobacteriaceae. Of the Staphylococcus aureus isolates tested, 75% were susceptible to gentamicin. Only 21% of all enterococcal strains tested were fully susceptible to gentamicin. Although intra-country variations in the prevalence of resistance phenotypes in Escherichia coli, Klebsiella spp., and Pseudomonas aeruginosa as well as in staphylococci and enterococci did occur, aminoglycoside resistance rates were generally higher in Italy, Portugal, Spain, Greece, France, the UK, and Poland than in Austria, Belgium, Germany, the Netherlands, and Switzerland. Compared with the 1987-88 data of the European Study Group on Antibiotic Resistance, gentamicin resistance has increased up to 5% in some gram-negative bacterial species. Furthermore, a greater than 10% increase in resistance to gentamicin has been seen in Staphylococcus aureus during the last decade. The reason for this observation is unclear, although changes in antibiotic prescribing patterns that result in increased selective pressure from gentamicin may have contributed to these increased rates of aminoglycoside resistance.