The enhanced distributed channel access (EDCA) of IEEE 802.11e has been standardized to support quality of service (QoS) in wireless local area networks (LANs). The EDCA statistically supports the QoS by differentiating the probability of channel access among different priority traffic and does not provide the deterministically prioritized channel access for highpriority traffic, such as voice or real-time video. Therefore, lower priority traffic still affects the performance of higher priority traffic. In this paper, we propose a simple and effective scheme called deterministic priority channel access (DPCA) to improve the QoS performance of the EDCA mechanism. To provide guaranteed channel access to multimedia applications, the proposed scheme uses a busy tone to limit the transmissions of lower priority traffic when higher priority traffic has packets to send. Performance evaluation is conducted using both numerical analysis and simulation and shows that the proposed scheme significantly outperforms the EDCA in terms of throughput, delay, delay jitter, and packet drop ratio under a wide range of contention level.