Our aims were three-fold: (1) to determine whether urinary KIM-1 and NGAL would be elevated during exposure to tobramycin in children with CF; (2) to determine whether the estimated glomerular filtration rate (eGFR) decreases with cumulative aminoglycoside exposure; and (3) whether any association exists between baseline urinary biomarker concentration and previous exposure. The gene discussed is HAVCR1; the disease is cystic fibrosis.