Broadcast is a common operation in mobile ad hoc networks (MANETs). Many on-demand ad hoc routing protocols resort to it to discover the route between any two nodes. It is also an important means to disseminate information in many MANET applications. An intuitive way for broadcast is flooding. However, without well-designed control mechanisms, flooding will lead to serious message redundancy, contention and collision. This paper proposes an efficient broadcast scheme based on the concept of connected dominating set (CDS) in graph theory. The proposed scheme can reduce message redundancy significantly, while retaining the merits of flooding. Simulation results show that the proposed scheme outperforms a distributed CDS-based algorithm and a cluster-based approach.