To assess the economic outcomes produced when a conventional antibiotic treatment regimen requiring three administrations per day was replaced with a treatment regimen requiring only one daily administration, the efficacy, tolerability and cost of ceftazidime was compared with that of ceftriaxone (both drugs in combination with amikacin) for the empirical treatment of febrile granulocytopenic patients with haematological malignancy. 102 febrile patient-episodes were randomly assigned to receive ceftazidime (6g in three divided doses) or ceftriaxone (2g as a single daily dose), both in combination with amikacin. The response was evaluable in 94 patients (47 in each group). 75 (80%) patients had an absolute granulocyte count lower than 100/mm(3) at the onset of fever or during the first week of antibiotic therapy. 61 (64.9%) were affected by acute leukaemia. Multiple daily ceftazidime plus amikacin was effective in 33 of 47 (70.2%) patients, and single daily ceftriaxone plus amikacin in 31 of 47 (66%) patients (p > 0.2). Among patients successfully treated, median time to defervescence was 3.3 days (range 1 to 11) for ceftazidime plus amikacin and 4.5 days for ceftriaxone plus amikacin (range 1 to 15) [p = 0.14]; study drugs were continued for 12 (range 7 to 26) and 12.3 days (range 7 to 28), respectively. Our study demonstrated that single daily administration of ceftriaxone was as effective and well tolerated as multiple daily administration of ceftazidime when both were administered in combination with amikacin. Cost analysis showed that compared with the thrice daily regimen, administration of single daily doses of ceftriaxone for a 12-day treatment period would result in a net cost saving of $US392 (626 940 Italian lire).