Amikacin sulfate was first used sparingly at our cancer center in 1976; since 1979, it has been the only aminoglycoside used for systemic cancer therapy for patients with granulocytopenia. As the development of resistance has been correlated with antibiotic use over time, we wished to determine if prolonged use of amikacin in our patients had led to increased amikacin resistance. A total of 1,129 strains were recovered from 315 patients during a 13-month period. Each species isolated per patient was considered once. Seven percent of the patients had amikacin-resistant strains (2.7% of isolates), and 10% of patients had gentamicin-resistant strains (4% of isolates). Amikacin resistance was significantly less than in an earlier study. Unrestricted use of amikacin has not led to a concomitant increase in amikacin resistance in gram-negative bacilli.