The purpose of this study is to evaluate the effects and clinical tolerance of an enteral diet containing 55% "AET" in the form of fat and only 28% in the form of H. C. in a group of 17 polytraumatized patients admitted to the Intensive Care Unit with assisted ventilation as a result of thoracic traumatism. The average age of the patients was 36.6 +/- 17 years, and they remained in Intensive Care for more than 10 days. Energetic requirements were estimated at 1,800 +/- 180 Kcal per day. Enteral intake commenced on day 4.5 +/- 1.2 and 90% of the estimated requirements was achieved at 8.5 +/- 2.9 days. Average duration of the Enteral Nutrition was 15 +/- 3.7 days, Tolerance of the diet was considered good and problems due to intolerance leading to suspension of the diet were mainly related to worsening of the clinical condition. The volumen per minute expired per Kg of weight descended gradually and assisted ventilation was removed at 16 +/- 5.4 days, 5 patients died, mainly due to septic problems. There was a significant improvement in surviving patients with regard to levels of transferrin (p less than 0.01), prealbumin (p less than 0.001) and RBP (p less than 0.05), and no improvement was observed in the patients who had died. The nitrogenated balance was positive from the ninth day onwards in surviving patients, and remained negative in the patients who had died. In conclusion, this enteral diet with a high intake of fats, showed good tolerance and is beneficial in patients with thoracic traumas which require assisted ventilation.