Compositions and methods for therapy of cystic fibrosis, asthma, and other conditions characterized by defective chloride transport are provided. The compositions comprise one or more compounds such as flavones and/or isoflavones, ascorbate and/or derivatives thereof capable of stimulating chloride transport in epithelial tissues. Therapeutic methods involve the administration (e.g., orally or via inhalation) of such compositions to a patient afflicted with cystic fibrosis, asthma, and/or another condition responsive to stimulation of chloride transport.