Abstract: In wireless networks, hidden terminal problem is common and leads to collision which makes it difficult to provide the required quality of multimedia services or support priority based services. To overcome these problems a directional antennas have been extensively used in designing MAC protocols for wireless network. Directional antennas provide many advantages over the classical antennas. In this paper, we show that directional antennas can be used effectively to solve a common hidden and exposed terminal problem by using an energy efficient MAC protocol for wireless sensor networks. This directional Antenna could be rotated in case of base station node to avoid directional hidden terminal problem.