In this survey, we studied the effect of extensive amikacin usage on the epidemiology of aminoglycoside resistance in a general hospital. The baseline resistance in the 12 months before amikacin was 5.8% for amikacin, 15.2% for gentamicin, 16.4% for tobramycin and 14.0% for netilmicin. During the following 44 months, amikacin was the aminoglycoside of first choice. In the first 2 years of this phase, resistance to amikacin did not change significantly. Later, amikacin resistance rose significantly, mainly due to the introduction of amikacin-resistant Enterobacter aerogenes strains. In general there was a significant decrease in resistance to gentamicin and tobramycin. Resistance mechanisms were examined in 380 strains. AAC(3)V, and AAC(6')I alone or coupled with ANT(2") or AAC(3) were the most prevalent enzymes. In the amikacin phase, we noticed a significant increase of strains harbouring the AAC(6')I enzyme, while strains with the AAC(3)V were less frequently isolated. Strains with permeability resistance did not become more prevalent during the period of extensive amikacin use