We report two cases of severe late-onset nosocomial pneumonia caused by Chlamydophila pneumaniae. The clinical course of the disease in these patients suggests that nosocomial pneumonia caused by this agent can lead to profound respiratory insufficiency and acute respiratory distress syndrome, particularly in patients with significant comorbidities and during the postoperative period. Intravenous azithromycin treatment was used to cure pneumonia in both of our patients.