We investigated the prevalence, incidence, and risk factors for pulmonary aspiration in all tube-fed adult patients over 6 months. Twelve aspiration events occurred among 276 patients (prevalence, 4.4%; 95% confidence interval, 2.2% to 7.6%). The incidence of aspiration was 2.4 per 1000 tube-feeding days (95% confidence interval, 1.2 to 3.9 per 1000). Despite 17% overall mortality, there was no excess mortality and little morbidity associated with aspiration. The major risk factors for aspiration were patient age (p less than .015) and location in the hospital (p less than .008): the probability of aspiration in the intensive care units (n = 113) was 0.9% compared with 4.9% on medical or surgical wards (n = 142), 16.7% among patients transferred from the intensive care unit to the ward (n = 18), and 33% among patients transferred from the ward to the intensive care unit (n = 3). Pulmonary aspiration is an uncommon and generally benign event among enterally supported patients. More frequent aspiration among ward than intensive care unit patients suggests that aspiration is not an inevitable consequence of severe illness, but can be prevented with adequate nursing care and pulmonary precautions. The fear of aspiration is not a sufficient cause to withhold enteral nutrition support in acutely ill patients.