Since the capabilities of MIMO systems was discovered, much research effort has been invested in this field. To exploit their significant capacity and diversity, space-time (ST) codes are the most promising technique for MIMO systems. However, in most applications, the channel state information (CSI) is assumed to be known to the receiver but unknown to the transmitter. To further improve the system performance, the transmitter will be able to adapt the transmission rate based on the level of CSI fed back from the receiver. Our overall goal in this thesis is to develop adaptive space-time schemes over the MIMO wireless channel.