In order to support different bandwidth allocation requirements from different applications, IEEE 802.16 standard suite defines two main polling modes, unicast polling and contention-based polling. Although the specification introduces four service classes to adaptively implement the polling mechanisms for different type of traffics, it does not specify exactly how these polling modes could be used for efficient bandwidth allocation. In this paper, we investigate the polling mechanisms in IEEE 802.16 networks, and propose a simple but efficient polling mechanism to improve the performance. The simulation results show that the proposed polling mechanism can utilize the uplink bandwidth efficiently and achieve better performance.