This paper introduces the reservation packet medium access control (RP-MAC) protocol for wireless sensor networks (WSNs). The protocol incorporates a periodic listen/sleep schedule to conserve energy and employs a novel channel reservation mechanism to enhance the rate at which packets can be transferred over multiple hops, thereby improving throughput and reducing end-to-end delay. To evaluate the performance of RP-MAC, it is compared with the established S-MAC protocol through simulation. Results show that RP-MAC can support much higher traffic loads as a direct result of its higher throughput capability along with reduced end-to-end delay for packet transmissions across a multi-hop link. These benefits come at the expense of higher energy consumption, but this is maintained at an acceptable level.