We read with interest the article by Quon et al1 in an issue of CHEST (July 2012) on the risks of post-lung transplant renal dysfunction in patients with cystic fibrosis (CF). We agree that patients with CF are at a heightened risk posttransplant for renal dysfunction secondary to pretransplant risk factors, including dehydration and chronic aminoglycoside use. In our own cohort of adult patients with CF, we have shown an increasing prevalence of renal dysfunction with declining lung function, particularly in patients approaching the need for lung transplantation assessment. Using the Cockcroft-Gault formula, 36 of 90 (40%) stable consecutive adult patients with CF attending our center had estimated creatinine clearance (CrCl)<90 mL/min/1.73 m2, (mean, 101.8 mL/min/1.73 m2, SD±28.5). Applying multivariate linear regression, estimated CrCl correlated with declining lung function (r=0.33, P=.002) but not with age, sex, BMI, or CF-related diabetes mellitus.