This paper presents the architecture and implementation of a single chip 25 Mbps Discrete Multi-Tone (DMT) modem. It forms the baseband processor for a 25 Mbps Wireless Local Area Network operating in the newly created 5 GHz U-NII band. The 243,000 transistor chip is implemented in 0.6 mu m TLM CMOS, occupies 5.1mm by 5.6mm, and is designed to run at 50MHz with a 2.5V supply.