Cognitive Radio is a promising technology for solving spectrum scarcity problem. Design of medium access control (MAC) protocols for Cognitive Radio Networks (CRN) is challenging due to the complexity involved in sensing and accessing the channel. Assuming Primary Users (PUs) to be passive, protocols based on 802.11 MAC has been proposed in the literature. In this paper, we propose a Cognitive Radio MAC protocol for Active primary users (CRMA) and compare it with the existing Cognitive Radio MAC protocol for Passive primary users (CRMP). Unlike CRMP, in the CRMA protocol PUs are assumed to be active, in the sense that PUs are aware of the SUs. PUs signal their intention to transmit over the channel through beacons before transmitting. This minimal change in the functionality of the PUs not only improves the spectrum utilization of the SUs but also decreases the interference to PUs. The performance of both the protocols are compared in terms of throughput, delay, interference to PUs, number of RTS collisions and number of dropped packets of SUs through extensive simulation. We also investigate the effect of packet length, transmission opportunity (TXOP) duration and block acknowledgement. Simulation results show that our proposed CRMA protocol gives better performance as compared to CRMP under certain conditions. © 2013 IEEE.