Current research suggests that a diet high in fish oil may be useful for immunomodulation in hospitalized patients. However, one of the side effects of fish oil is a prolongation of the bleeding time, specifically by reducing platelet aggregability. Although this effect might be beneficial for patients with cardiovascular disease, it would be a potential concern in certain critically ill patients. To address this concern, we conducted a prospective study of platelet aggregation in 16 surgical patients who were randomly assigned to receive either a diet containing 16.5 g of fish oil in 1500 ml (Impact) or usual care (standard enteral formulas devoid of fish oil). Feeding was successfully accomplished in the patient group receiving a diet that provided approximately 14.2 g of fish oil/day for 1 wk without significantly affecting platelet aggregability. Thus, it appears that, over the short term, this dose of fish oil does not alter platelet function in hospitalized surgical patients.