The aim of the study was to evaluate the effect of intensive use of amikacin on the resistance levels to amikacin, gentamicin, tobramycin, netilmicin and dibekacin. The base-line resistance in the preamikacin phase (three months of amikacin use less than 1%; 676 isolates) was 1.0% for amikacin, 11.4% for gentamicin, 8.0% tobramycin, 6.2% for netilmicin and 8.3% for dibekacin. During the amikacin phase (36 months of average amikacin use of 89%; 6048 isolates) there was no significant change in aminoglycoside resistance except for dibekacin (from 8.3% to 10.9%, 0.05 greater than p greater than 0.02). Isolated amikacin resistance was not observed