Pulmonary infections occurred in 10 of 18 patients undergoing cardiac transplantation at the Stanford Medical Center and contributed to the death of 4 patients. A variety of organisms have been responsible including both aerobic and anaerobic bacteria, fungi, protozoa, and viruses. Although the roentgenographic findings were nonspecific, bacterial pneumonias were generally associated with local infiltrates or consolidations, while cavities were present in all instances of isolated aspergillosis. The value of frequent roentgenograms is emphasized since, after the first postoperative month, all pulmonary abnormalities other than vascular congestion were caused by infection. The value of needle aspiration lung biopsies for establishing a diagnosis is emphasized. Application of this technique for direct intracavitary antifungal therapy has been apparently successful in 1 patient to date.