Fifty cardiac transplant recipients were followed over a 34-month period for evidence of pneumonia that developed in twelve patients. Potential risk factors evaluated fell into three categories: demographic (age, sex, race, and underlying cardiac disease); pretransplant status (hospitalized, intubated, pulmonary infiltrate, requirement for antibiotics, or the need for a ventricular assist device); and posttransplant therapy (amount and type of blood products, prolonged endotracheal intubation or reintubation, use of ventricular assist devices, immunosuppressive protocols, lymphocyte subset ratios, and occurrence of rejection, leukopenia, or CMV infection). The Cox proportional hazards model identified posttransplant reintubation (P = 0.009) and the use of protocols employing larger steroid dosages (P = 0.02) as significant risk factors for pneumonia. In a separate analysis, the occurrence of pneumonia was shown to be a significant risk factor for mortality (P = 0.018).