Wireless sensor networks are rapidly becoming a platform for applications such as battlefield monitoring, intelligence gathering, environmental monitoring, and emergency response. Inherent in these applications is a priority and urgency of the information or messages. This means the messages must be delivered in a timely manner for them to be useful. This research assigns a message priority level and provides high priority messages quicker access to the channel. Using MICA2 sensors and a modified Media Access Control (MAC) layer, real-time message End-to-End (ETE) delay was reduced by 50 percent. Coupled with this decrease in delay, these same real-time messages also had a significantly higher on-time delivery rate compared to an unmodified system. At the highest loading levels, high priority messages experienced a 45 percent higher on-time delivery rate than the baseline system. These performance improvements were obtained without any impact on throughput for other message types and without the added overhead of channel reservation or system synchronization required by other protocols.