High rates of colonization and the challenge of managing Pseudomonas aeruginosa infections in patients with cystic fibrosis (CF) have necessitated a search for safe and effective antibiotics. Currently, therapy with an aminoglycoside in combination with a beta-lactam or a quinolone antibiotic is the standard. Unfortunately, it is difficult to deliver high doses of these antibiotics via the IV route without significant systemic adverse events (AEs) (eg, ototoxicity and nephrotoxicity). Recently, a reformulation of the aminoglycoside antibiotic tobramycin has become available in a preservative-free, pH-adjusted solution for inhalation by jet nebulizer. A 96-week series of clinical studies including 520 patients, aged > or = 6 years, with moderate-to-severe CF has evaluated the long-term safety and effectiveness of this formulation. Patients received tobramycin solution for inhalation (TSI) or placebo, which was administered in alternating cycles of 28-days-on and 28-days-off therapy, plus their usual CF care for 6 months with open-label follow-up extended to 2 years. Most AEs declined in frequency with increasing TSI exposure. Patients receiving TSI spent 25 to 33% fewer days in the hospital. Following the initiation of TSI treatment, patients experienced significant increases in FEV(1). FEV(1) values were maintained above baseline for the duration of the study series. Antibiotic susceptibility of the bacterial isolates did not predict clinical response. TSI was safe, well-tolerated, and effective for long-term treatment (96 weeks) of P aeruginosa colonization and infection in CF patients.