Objective: The aim of this study is to evaluate the usefulness of lung ultrasound in assessment of lung aeration and to follow up Recruitment Maneuver in ARDS patients. Methods: A total of 40 patients with ARDS were given the standard sustained inflation recruitment manoeuvre. The utility of lung ultrasound in assessing lung aeration and lung recruitment was evaluated using the Lung Ultrasound Score, PO2, PO2/FIO2, and lung compliance before and after recruitment. Results: RM with sustained inflation technique lead to an improvement in lung compliance and PO2/FIO2 in studied ARDS patients (P< .05) LUS decreased from (25.3±6.3) before RM to (17.4±6.5) after RM with a (p value ≤ 0.001), and after 12 hours it significantly decreased to (15.38±8.62) with a (p value ≤ 0.001), there is a significant negative correlation between LUS and PO2/FIO2, also a strong negative correlation between LUS and lung compliance. Conclusion: Bedside ultrasonography can be used in the evaluation and management of mechanically ventilated patients in intensive care units, also to assess lung aeration and the effectiveness of the recruitment maneuver in ARDS patients.