In this paper, we address the issue of transmission power control in wireless ad-hoc networks. In general, it is assumed that the minimum transmission power required to keep the network connected achieves the optimal throughput performance in an ad-hoc network. In contrast, we show that using the minimal transmission range might not always result in optimal throughput performance. Using both throughput and throughput per unit energy as the optimization criteria, we demonstrate that the optimal transmission power is generically a function of the number of stations, the network size, and the traffic load. In particular, we observe that the optimal power is a function of the network load for typical network scenarios. To analyze these observations, we present an analytical model for throughput as function of the transmission power. The throughput model supports the results of our observations, i.e. for specific load conditions throughput is proportional to transmission power in typical ad-hoc networks. We conclude that the transmission power should be adaptive to the specific conditions in an ad-hoc network in order to maximize throughput performance.