Information theoretical study shows that multiple-input multiple-output (MIMO) systems have a much higher channel capacity than single-input single-output (SISO) systems, which can be characterized as a multiplexing gain. Adaptive modulation and coding (AMC) is proven to be an effective technique to approach the channel capacity by utilizing the channel state information (CSI) at the transmitter. In this paper, following an analysis of the multiplexing gain of a generic AMC MIMO system, we propose an adaptive coded MIMO system that achieves a near-full multiplexing gain as well as a robust BER performance in an outdated CSI environment. A comparison among various adaptive and non-adaptive MIMO systems reveals the proposed system as a good trade-off between the spectral efficiency, BER and system complexity.