Mobile Ad-hoc NETwork (MANET) is a self configuring network composed of mobile nodes without any fixed infrastructure. Group communications are important in Mobile Ad hoc NETworks (MANET). Multicast is an efficient method for implementing group communications. But, it is big challenge to implement the well-organized and scalable multicast in MANET due to the difficulty in group membership scheme and multicast packet forwarding over a dynamic topology. EGMP uses a virtual-zone-based structure to implement scalable and efficient group membership scheme. A zone based bi-directional tree is constructed to achieve more efficient membership management and multicast delivery.