In this paper we address the design of a multiple transmit antenna system in which the Channel State Information (CSI) at the transmitter is not perfect. Two different approaches are analyzed one based on the Minimization of the Mean Square Error (MMSEj and the other based on the application of the Maximum Likelihood Sequence Estimation (MLSE). In both cases a Bayesian criterion is used in order to take into account the error between the CSI and the real channel. Finally, some simulation results and conclusions are provided, showing which is the gain of these approaches when the error between the CSI and the real channel is either Gaussian or uniform, where this last case corresponds to a quantization of the channel time response in order to transmit the CSI through a feedback channel from the receiver to the transmitter.