Ninety-two patients with cancer with 100 infectious episodes were treated with netilmicin sulfate, a new aminoglycoside. Netilmicin was administered intravenously, either intermittently or by continuous infusion. The overall cure rate was 60%. Gram-negative bacilli were the most common causative organisms and the response rate for these infections was 32/53 (60%). The most common pathogens were Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Pneumonia, urinary tract infection, and septicemia were the most common types of infection treated and the response rates were 23/47 (49%), 19/21 (90%), and 9/17 (53%), respectively. Nephrotoxicity occurred in ten patients (6%) who had normal renal function initially. Netilmicin is an effective aminoglycoside with a spectrum of antibacterial activity similar to that of gentamicin sulfate and it appears to be less nephrotoxic.