Various antibiotic combinations has been studied in a clinical trial in febrile, neutropenic children in the Pediatric Hematology-Oncology Department Istanbul Medical School, in 1985-1986 (first 6 months). In the first group, cephazoline (50-150 mg/kg/day), Gentamycin (3-7 mg/kg/day), Carbenicillin (150-400 mg/kg/day) combination was applied to 36 cases. This combination was effective in 58.34 % of the cases. In the second group, Cefotaxime (50-150 mg/kg/day), Tobramycin (4-5 mg/kg/day) combination was applied to 8 cases. This combination was effective in 75 % of the cases. In the third group, Ceftriaxone-Amikacin combination is still being applied and will be reported later. As a seperate group. 8 cases with severe infections, were given Cephalosporins(3 rd generation)+Aminoglycosides + Carbenicillin. This combination was effective in 62.5 % of the cases. As a conclusion Cefotaxime 1 Tobramycin was the most effective combination, but every new antibiotic combination must be tried for these infections.