Embodiments of legacy compatible spatial multiplexing systems and methods are disclosed. One method embodiment, among others, comprises receiving long training symbols and cyclic shifted long training symbols corresponding to legacy preamble portions of packets corresponding to first and second transmit signals, receiving long training symbols and inverted cyclic shifted long training symbols corresponding to spatial multiplexing portions of packets corresponding to first and second transmit signals, and combining the symbols corresponding to the first and second transmit antennas to estimate the respective channels.