The use of directional antennae in ad-hoc networks has received growing attention in recent years because of the benefits including, high spatial reuse, higher antenna gains, etc. At the same time, using directional antennae introduces new challenges. For example, the problem of deafness where receiver nodes may not hear handshake messages because their antennae beams are not pointing in the direction of the sender. To address these issues, new directional MAC protocols are required. In the literature, the existing directional MAC protocols assumed that nodes can operate in both directional and omni-directional modes. However, using both directional and omni-directional modes of operation leads to the asymmetry-in-gain problem and defeats the purpose of using directional antennae. In this thesis, we propose a directional-to-directional (DtD) MAC protocol where both the sender and the receiver operate in directional mode only. The first part of our design studies the issues related to directional MAC protocols and we use this knowledge to carefully design the DtD MAC protocol. The DtD MAC protocol is fully distributed, does not require synchronization, eliminates the asymmetry-in-gain problem and alleviates the problems due to deafness. To evaluate the performance of the DtD MAC protocol, we build an analytical model that measures the saturation throughput of the DtD MAC protocol in terms of the number of nodes contending for the channel, the packet payload size and the antennae beamwidth. The analytical results were verified through extensive simulations. We show that the DtD MAC protocol can provide significant throughput improvement in ad-hoc networks if the number of antennae sectors is chosen appropriately. Furthermore, we study the fairness of DtD MAC using Jain's Fairness Index. Finally, the performance of the DtD MAC protocol is evaluated for the high data rate Millimeter Wave (mmWave) technology. The results obtained are promising and show that DtD MAC can improve the performance of networks using such high data rate technologies.