The study will be conducted as a randomized, double blind, placebo-controlled, repeat dosing trial evaluating the effects of 28 days of digitoxin on IL-8 and neutrophil concentrations in induced sputum in subjects with mild to moderate cystic fibrosis lung disease. Twenty-four total patients will be randomized into 3 groups of 8 subjects each (0.05 mg or 0.1 mg digitoxin or a placebo).