Diabetes mellitus is often identified as an independent risk factor for developing lower respiratory tract infections. Pulmonary infections, such as those caused by Mycobacterum tuberculosis, mucor, Staphylococcus aureus, and gram-negative bacteria may occur with an increased frequency whereas infections due to Streptococcus pneumoniae, Legionella, and influenza may be associated with increased morbidity and mortality. The predisposition to lower respiratory tract infections may represent alterations in pulmonary host defenses at several levels. The purpose of this article is to review the spectrum of pulmonary infections encountered in the diabetic patient, focusing on predisposing defects in pulmonary host defense, highlighting characteristic clinical features, and discussing diagnostic approaches, therapeutic interventions, and prophylaxis in this patient population.