A 32-year-old woman presented with recurrent pneumonia that had started 6 months after her delivery. She was admitted for evaluation of the cause and treatment of the pneumonia. She had no history of smoking or chronic sinusitis. The sputum culture tested positive for the pathogen Moraxella catarrhalis, which commonly colonizes the upper respiratory tracts of infants. She was administered antibiotics for a total of 4 weeks, mainly ampicillin/sulbactam 3g, four times a day. Consequently, the area of consolidation on the left lung completely disappeared. However, the shadow reappeared, only after 6 days after cessation of antibiotics. We could not find any deficiency in humoral immunity or cell-mediated immunity, nor any abnormality in the bronchopulmonary structures. Electron microscopic examination of multiple bronchial biopsy specimens obtained from within and outside the areas of consolidation revealed a defect in both the inner and outer dynein arms of the mucosal cilia and microtubular disarrangement. This led to the diagnosis of primary ciliary dyskinesia. Consequently, low-dose erythromycin (200mg twice daily) was started, after which pneumonia did not recur. Exposure to the newborn may have triggered the recurrent pneumonia.