Multicasting has emerged as one of the most focused areas in the field of networking. As the technology and popularity of Internet grow, applications, such as video conferencing, that require multicast feature are becoming more widespread. Another interesting recent development has been the emergence of dynamically reconfigurable wireless ad hoc networks to interconnect mobile users for applications ranging from disaster recovery to distributed collaborative computing. In this paper we describe On-Demand Multicast Routing Protocol (ODMRP) for mobile ad hoc networks. ODMRP is a mesh-based, rather than a conventional tree-based, multicast scheme and uses a forwarding group concept (only a subset of nodes forwards the multicast packets via scoped flooding). It applies on-demand procedures to dynamically build routes and maintain multicast group membership. We also describe our implementation of the protocol in a real laptop testbed.