We propose a new power-control protocol for medium access control (MAC) in mobile ad hoc networks. Compared with the IEEE 802.11 approach, the proposed protocol achieves significant improvement in both throughput and energy consumption. The protocol relies on dynamic adjustment of the data-packet transmission power, while maintaining a fixed (maximum) transmission power for control (RTS/CTS) packets. Furthermore, it allows nodes to control the transmission power of the route request (RREQ) packets, which indirectly influences the next-hop selection at the upper routing layer. This is done by dynamically computing a node-dependent connectivity set. RREQ packets are broadcasted only to nodes within the connectivity set The connectivity set guarantees the node's connectivity to the rest of the network, while at the same time enabling a simple (minhop) routing algorithm to provide power-efficient routes. Channel gain and directional information obtain from overheard RTS/CTS exchanges are used to compute the connectivity set Our protocol allows for concurrent yet interference-limited transmissions to take place in the vicinity of a receiver. A modified RTS/CTS exchange allows nodes to broadcast their interference margins and requested transmission powers.