A space-time coded orthogonal frequency-division multiplexed (STC-OFDM) system is proposed to transmit layered video signals over wireless channels. The space-time coding can provide a diversity gain for the multiple-antenna system while OFDM can alleviate the frequency-selective fading effect. An input video sequence is compressed and partitioned into layers with different priorities. Then, an unequal error protection scheme based on the product Reed-Solomon (RS) codes is employed to provide different levels of protection to different layers. At the receiver, a minimum mean square error (MMSE) detector with interference cancellation (IC) is integrated with the space-time decoder to reconstruct the desired signal effectively. We derive an analytic bound for the error probability, and conduct experiments for the transmission of the H.263 video bitstream. It is shown that the proposed scheme enhances the PSNR performance significantly in the environment with a moderate signal-to-noise ratio.