Aminoglycosides are important antibacterial agents for treatment of serious gram-negative bacillary infections including lower respiratory tract infection. Once-daily aminoglycosides result in higher peak and lower trough plasma concentrations than conventional multiple daily dosing regimens; once-daily aminoglycoside therapy is equally effective, generally less toxic and much less expensive and therefore this regimen is more and more frequently used for treatment of suspected or confirmed gram-negative bacillary infections and of febrile episodes in neutropenic patients, in particular in combination with an appropriate betalactam antibiotic. Despite the lack of studies on this topic, once-daily aminoglycosides in combination with a betalactam agent can be used in subjects with lower respiratory tract infection, including patients with cystic fibrosis, in which tobramycin appears to be the aminoglycoside antibiotic of choice.