The efficacy and safety of the two antibiotic combinations, ceftazidime plus amikacin and ceftriaxone plus amikacin were compared in an open randomized trial. 100 episodes of neutropenia caused by malignant diseases and/or cytostatic drugs were evaluated in 66 males and 34 females with a mean age of 49.4 years. The types of infections treated were: septicemia 38, fever of undetermined origin 26, pneumonia 13, ear, nose and throat infections 11 and others 12. 17 episodes were not evaluable (6 protocol violations, 6 doubtful infections and 5 non-bacterial infections). The overall results were comparable, with a 74% success rate for ceftazidime and a 70% rate for ceftriaxone (criteria of the European Organization for Research and Treatment of Cancer). In the patients with septicemia, the success rate was 64% in the ceftriaxone and 57% in the ceftazidime group. Eight patients died during the treatment, in 5 cases due to infectious complications. There were no differences between the two groups in respect of efficacy or toxicity.