Background: At the present time, the optimal timing and use of enteral nutrition for mechanically ventilated medical patients is unknown. The current study will focus on the effect of early versus delayed enteral nutrition in critically ill mechanically ventilated medical patients. Aim of Study: To compare between early versus delayed enteral feeding in Invasive Mechanical Ventilation (IMV) patients. To assess association linking early nutrition (<48 hours after intubation), feeding route and calorie intake to mortality and risk of Ventilator Associated Pneumonia (VAP) in patient with Invasive Mechanical Ventilation (IMV). Patients and Methods: Patients will be scheduled to received their estimated total daily enteral nutritional requirements on either day 1 (early-feeding group) or day 5 (latefeeding group) of mechanical ventilation. Patients in the latefeeding group will be also scheduled to receive 20% of their estimated daily enteral nutritional requirements during the first 4 days of mechanical ventilation. Thirty (50%) consecutive eligible patients will be entered into the early-feeding group and thirty (50%) patients will be enrolled in the late-feeding group. All patients will be received enteral nutrition via continuous infusion by a feeding pump. Eligible patients will be followed in ICU for a maximum of 12 days or until death or discharge from ICU. Results: Logistic regression analysis shows that; after applying (forward method) and entering some predictor variables; the increase in BMI and late feeding technique; had an independent effect on increasing the probability of mortality occurrence; with significant statistical difference (p <0.05 respectively). The increase in BMI and late feeding technique; had an independent effect on increasing the probability of VAP occurrence; with significant statistical difference (p <0.05 respectively). By using ROC-curve analysis, early enteral feeding predicted shortening of hospital stay, with failed (64%) accuracy, sensitivity=63% and specificity=63% (p < 0. 05). Conclusion: Evidence shows improvement in patient outcomes associated with the use of EEN in a diverse population of critically ill patients. The results of our study strengthen our understanding of the benefits of EEN.