This paper presents the results of experiments to study throughput behavior and determine the maximum attainable throughput in an 802.11g wireless LAN under UDP traffic. The focus is on observing the measured throughput over time when the network is flooded with a continuous stream of UDP data. Whereas previous studies investigate 802.11b/a performance, or use analytical or simulation methods to study 802.11g performance, this study measures the throughput by generating actual 802.11g traffic. In order to study 802.11g behavior exclusively, minimize environmental effects, and keep the network as simple as possible, the experimental setup is restricted to an isolated wireless LAN with a single access point configured for 802.11g operation. The studies show that in almost all cases the observed throughput is well below 50% of the 802.11g maximum data rate of 54 Mbps even under ideal and controlled conditions. Although network card implementation and use of RTS/CTS have a significant impact on throughput, access point distance has little effect. We also give a formula for computing the expected throughput and compare the values it gives with the measured values.