Résumé : Three combinations of antibiotics (cephalothin tobramycin, cephalothin ticarcillin, and ticarcillin tobramycin) were administered empirically to 186 patients with cancer who were suspected of having a life threatening infection. In approximately one half of these patients, gram negative infection was documented bacteriologically and consisted of septicemia in 50% of these patients. The three antimicrobial regimens were similarly effective and resulted in a favorable clinical response in approximately 55% of the patients. The administration of the cephalothin tobramycin combination was associated with a significantly higher frequency of nephrotoxicity than that of the other two regimens.