CSMA/CA MACs for mobile ad hoc networks (e.g. the 802.11 suite)exhibit an unstable behavior (i.e., their throughput goes to zero under high load)in the presence of hidden nodes. In this paper, we show that even the simplest Multi-User Detection (MUD)-enabled radio can mitigate the MAC's loss-of-state, which is the culprit of the MAC instability. Thus, a MUD-enabled CSMA MAC-with just a few modifications-can significantly reduce the instability associated with CSMA/CA MAC and achieve high throughput even under very high traffic load. High fidelity simulation results, with a radio model that includes important technological constraints, are presented for both a simple idealized topology as well as for a very realistic scenario. In both cases, it is shown that the combined CSMA/CA MAC and MUD radio system is able to achieve high throughput with much improved stability.