Performance measurements of IEEE 802.11 access points provide important information for networking research and network management. In this paper, we present an active measurement method to determine the maximum saturation throughput of wireless LAN access points. The saturation throughput is achieved when there always is a frame ready to transmit, and it reaches the maximum for optimal transmission conditions. We use the proposed method to measure and analyze the performance of five IEEE 802.11b access points. The results show the strength of our method and identify performance characteristics of commercial access points. The analysis produces the following results. The maximum saturation throughput shows significant differences between models. Increasing the offered load to the access point?s Ethernet interface does not always increase the throughput; a few access points present a downlink throughput reduction when the offered load exceeds their bridging capabilities. Some access points exhibit better performance in certain orientations.