This study assesses the aerosol delivery characteristics (measured by in vivo lung deposition, nebulization time, serum tobramycin concentrations, and pharmacokinetic parameters) and safety of tobramycin inhalation solution administered for inhalation by PARI eFlow rapid electronic nebulizer (no compressor) vs. PARI LC PLUS Jet Nebulizer (with compressor) in healthy subjects and in subjects with cystic fibrosis.