In this paper, we propose a new medium access control (MAC) protocol, called cooperative access with relay's data (CARD) for multi-rate wireless local area networks (WLANs). CARD allows remote nodes to transmit their information at a higher data rate to access point (AP) by using intermediate nodes as relays. Particularly, under CARD, a relay node sends its own data packet after forwarding a packet from the original source node, thus to improve system throughput. Analytical and simulation results show that the CARD protocol can effectively improve system throughput and reduce service delay.