The IEEE 802.11x MAC protocol, the de facto standard for wireless LANs, includes a distributed coordination function (DCF) mode usable for ad hoc network architectures. The Transmission Control Protocol (TCP) is commonly used on top of this MAC for reliable transport. TCP?s congestion control scheme assumes highly reliable frame transmission at the link layer. Unfortunately, this assumption does not hold in multi-hop wireless network scenarios, leading to severe performance degradation. In this paper we study the interactions between the TCP and 802.11b MAC protocols, and examine the effects of different TCP and 802.11b parameters on the throughput achieved. Using simulations and analysis, we highlight the causes of performance degradation when TCP is used over 802.11b MAC in a multi-hop wireless scenario.