To accomplish these aims, we propose a Phase I/II open-label study of sodium nitrite in CF. Key inclusion criteria include individuals over the age 18 with cystic fibrosis as documented by clinical features of CF, and genotyping or a positive sweat test. Study participants must additionally have had 2 positive respiratory cultures for Pseudomonas aeruginosa within the past 12 months. Exclusion criteria include advanced lung disease, inability to discontinue inhaled antibiotics for eight weeks, hospitalization or medication change within 4 weeks of dosing, baseline systemic hypotension (SBP<90 mm hg), chronic kidney disease (Cr >2.5), severe anemia (Hgb <9 gm/dL in the last six months). The primary outcome is safety, defined as FEV1 measured before and after initial doses on days 0 and 7, and at week 4. Other safety data for the initial doses include pulse oximetry and transcutaneous methemoglobin levels. Secondary endpoints include quantitative sputum cultures, exhaled nitric oxide, sputum nitrite concentration, and patient symptoms as assessed by a CF specific respiratory questionnaire.