Inclusion Criteria:

• Age at least 6 months and less than 6 years
• Diagnosis of cystic fibrosis with 2 clinical features consistent with CF and confirmed by either sweat chloride >= 60 mEq/L (by quantitative pilocarpine iontophoresis) or by genotype with 2 identifiable mutations consistent with CF.
• One throat or sputum microbiology culture positive for Pseudomonas aeruginosa (Pa) within 2 weeks to 12 months prior to screening.
• Informed consent by parent or legal guardian.

Exclusion Criteria:

• History of adverse reaction to anesthesia or sedation.
• History of aminoglycoside hypersensitivity.
• History of unresolved anemia (hematocrit < 30%) or thrombocytopenia (platelet count < 100,000/mm3).
• History of hemoptysis with 30 days prior to screening.
• History of abnormal renal function (serum creatinine > 1.5 times the upper limit of normal for age).
• History of clinically documented chronic hearing loss.
• Administration of any investigational drug within 30 days prior to screening.