Due to rapid advances in wireless network technologies, and the maturity of portable communication devices, ubiquitous wireless computing has become increasingly popular. One of the most important issues in ubiquitous wireless computing is the reduction of power consumption of the portable devices. In this study, we propose a traffic-aware power-saving protocol for IEEE 802.11 multi-hop ad hoc networks. In the proposed protocol, the mobile stations determine their sleep-awake patterns based on a quorum approach. In general, the length of the quorum cycle is an important factor in the sleep-awake ratio, and will determine the power consumption ratio. In light of this observation, the proposed protocol dynamically adjusts the length of the quorum cycle by considering the network utilization during its previous quorum cycle. Simulation results show that our proposed protocol can effectively reduce power consumption in mobile Ad Hoc networks.