A novel distributed power control (DPC)⋅ scheme and a MAC protocol for wireless ad hoc networks in the presence of radio channel uncertainties such as path loss, Shadowing and Rayleigh fading is presented. The DPC quickly estimates the time-varying nature of the channel and uses the information to select a suitable transmitter power value in order to maintain a target Signal-to-Interference ratio (SIR) at the receiver. The standard assumption of a constant interference during a link's power update used in other works is relaxed. The performance of the proposed DPC is demonstrated analytically. The power used for all RTS-CTS-DATA-ACK frames is selected using the proposed DPC; hence, energy savings and spatial reuse are achieved. The hidden-terminal problem is overcome by periodically increasing the power. The NS simulator is used to compare the proposed scheme with 802.11. The proposed MAC protocol renders a significant increase in throughput in the presence of channel variations compared with 802.11 while consuming low energy per bit.