The incidence of upper gastrointestinal (GI) bleeding in mechanically ventilated ICU patients receiving enteral alimentation was reviewed and compared to bleeding occurring in ventilated patients receiving prophylactic antacids or cimetidine. Of 250 patients admitted to our ICU during a 1-yr time period, 43 ventilated patients were studied. Patients in each group were comparable with respect to age, respiratory diagnosis, number of GI hemorrhage risk factors, and number of ventilator, ICU, and hospital days. Twenty-one patients had evidence of GI bleeding. Fourteen of 20 patients receiving antacids and 7 of 9 patients receiving cimetidine had evidence of GI bleeding. No bleeding occurred in 14 patients receiving enteral alimentation. Complications of enteral alimentation were few and none required discontinuation of enteral alimentation. Our preliminary data suggest the role of enteral alimentation in critically ill patients may include not only protection against malnutrition but also protection against GI bleeding.