A 3 arm prospective randomized trial was designed to compare the effectiveness of aztreonam (AZT) + clindamycin (CLDM), amikacin (AMK) + AZT and CLDM + AMK as antibiotic therapy for fever in patients with hematological disorders. Between July 1987 and June 1988, one hundred and sixty of the 199 febrile episodes entered in this study were evaluated for response. Underlying diseases were hematological malignancies in 88.8% of the subjects, and there was no statistically significant differences in incidences of the diseases among the 3 groups. Efficacy rates were 64.2% in the AZT + CLDM group, 52.8% in the AMK + AZT group and 35.2% in the CLDM + AMK group. Efficacy rates in those with neutrophil counts was less than 500/microliters before starting the antibiotics were 53.3%, 43.8% and 25.0%, respectively, in the 3 groups. The combination of AZT + CLDM was found to be the most effective even in the treatment of infections associated with febrile neutropenic patients.