Performance of data communication systems over wireless channels is severely degraded by the multipath fading effects. Space-time codes exploit the channel capacity increase by using multiple transmit and/or receive antennas. This ensures space diversity without expanding the required transmission bandwidth. A type of space-time codes, namely orthogonal transmit diversity (OTD), has recently attracted much attention. This scheme has low complexity and can achieve maximum diversity. However, error performance of OTD systems decreases in the absence of perfect channel state information at the receiver. In this paper, we present an enhanced power control scheme for OTD systems with two transmit and multiple receive antennas. Simulation results have been presented to show the performance improvement.