This paper presents a channel estimation scheme for multiple-input multiple-output with orthogonal frequency-division multiplexing (MIMO-OFDM) in fast varying Rayleigh channels. To handle rapid variation of channels within a transmission block, we propose a novel maximum a posteriori probability-based channel estimation scheme using pilot symbols. With the estimate of the channel matrix for the current symbol interval, a zero-forcing (ZF) receiver is applied to detect the spatially multiplexed data. In simulation results, the effectiveness of the proposed method is shown, as compared with the polynomial and the perfect channel estimates.