Tobramycin and ticarcillin has been compared to ceftazidime in a clinical study on immunocompromised patients with febrile episodes. In the tobramycin and ticarcillin group (A) 70 febrile episodes occurred (10 being unassessable) in 43 patients of which 16 (23%) were bacteriologically positive. Forty-three episodes occurred during neutropenia. In the ceftazidime group (B) 54 febrile episodes (6 being unassessable) were treated in 34 patients. Eleven (20%) were bacteriologically positive and 30 episodes occurred during neutropenia. Clinical cure in group A occurred in 39 episodes, 65% of assessable cases. Cures in group B numbered 27 out of 54 episodes (56% of assessable cases). Clinical failure among evaluable cases, that is no decrease in fever in three days, was 22% in group A and 31% in group B. These results, within the limitation of the study, suggest that ceftazidime given alone at a dosage of 1 g tds is not significantly worse than tobramycin 120 mg tds plus ticarcillin 2 g tds.