Reduction of tidal volume to limit plateau pressure currently is recommended for the ventilatory management of acute respiratory distress syndrome. However, sufficient evidence now exists to support the fact that excessive reduction in tidal volume may result in harmful alveolar derecruitment depending on the level at which positive end-expiratory pressure is set. The use of recruitment maneuvers has been proposed as an adjunctive lung-protective strategy to reverse low tidal volume-related derecruitment. Many questions remain regarding the basic physiologic principles of recruitment, and, therefore, the optimal way to perform recruitment maneuvers remains unknown. Moreover, apart from physiologic studies suggesting a potential benefit of recruitment maneuver in terms of recruitment and gas exchange, no data are yet available that demonstrate the ability of such a maneuver to improve outcome. In this article, we discuss the physiologic rules governing recruitment and derecruitment and review articles that provide new insights in the field of recruitment maneuver.