This paper presents a distributed MAC layer protocol, Prioritization by Urgency - DCF (PU-DCF), which incorporates explicit support for real-time traffic in ad-hoc wireless networks. In PU-DCF, a packet?s priority is updated dynamically according to its priority level and urgency (or laxity). Two Collision Resolution Algorithms (CRAs) are proposed to guarantee timely delivery of packets. Simulations show that the proposed protocol performs well for Hard Real-Time (HRT) traffic and has stable performance even when the channel is overloaded. Furthermore, several simulation scenarios are designed to discuss the effect of several system parameters and compare the performance of the two CRAs.