Rationale: Pulmonary nontuberculous mycobacterial disease (PNTM) has increased over the past several decades, especially in older women. Abnormal mucociliary clearance and abnormal nasal nitric oxide (NO) have been associated with PNTM disease in other patient cohorts. Mucociliary clearance can be affected by NO-cGMP signaling, and therefore modulation of the pathway may be possible with phosphodiesterase inhibitors such as sildenafil as a novel therapeutic approach. Objective: To define ex vivo characteristics of pulmonary nontuberculous mycobacterial disease affected of sildenafil. Methods: Subjects with PNTM infections were recruited into an open-label dose escalation trial of sildenafil. Laboratory measurements and muccociliary measurements: ciliary beat frequency, nasal nitric oxide, and 24-hour sputum production, were collected throughout the study period. Patients received sildenafil daily during the study period, with escalation from 20 mg to 40 mg three times daily. Measurements and Main Results: Increased ciliary beat frequency occurred after a single dose of 40 mg sildenafil and after extended dosing of 40 mg sildenafil. The increase ciliary beat frequency was not seen with 20 mg sildenafil dosing. There were no changes in sputum production, nasal nitric oxide production, Quality of Life- Bronchiectasis- NTM module (QOL-B-NTM) questionnaire, or the St. George’s Respiratory Questionnaire during the study period. Conclusion: Sildenafil, 40 mg, increased ciliary beat frequency acutely as well as with extended administration.