Mobile ad hoc networks (MANETs) are useful in environment where fixed network infrastructure is unavailable. To function normally, MANETs demand an efficient and distributed medium access control (MAC) protocol. However, characteristics of MANETs such as radio link vulnerability, mobility, limited power pose great challenges on MAC design. Through this report, firstly identifying the challenges that are facing MAC in MANETs. Then presenting discussion on the problems with IEEE 802.11, especially those relevant in a singlehop and multihop networks and various techniques that have been proposed to enhance the channel utilization of wireless networks.