A Traffic-adaptive MAC protocol (TaMAC) for a Wireless Body Area Network (WBAN) is presented in this paper. The idle listening and overhearing problems are solved by exploiting the traffic information of the nodes. The protocol is supported by a traffic-based wakeup mechanism and a wakeup radio mechanism that are used to accommodate normal, emergency, and on-demand traffic in a reliable manner. Analytical expressions are derived to analyze and compare the performance of the TaMAC protocol with the WiseMAC, SMAC, and the beacon-enabled IEEE 802.15.4 MAC protocols. Results derived from the analytical expressions are validated by simulation results. It is shown that the TaMAC protocol outperforms all other protocols in terms of power consumption and delay.