The Doppler shift of fast-fading channels will generate intercarrier interference (ICI) and, hence, degrade the performance of orthogonal frequency-division multiplexing (OFDM) systems. In this paper, a novel channel-estimation and data-detection method for OFDM systems over the fast-fading dispersive channels has been proposed and investigated. A new pilot pattern is also proposed, and it is composed of a comb-type pilot pattern and a grouped pilot pattern. The required number of pilot subcarriers is, therefore, significantly reduced compared with that of using the grouped pilot pattern only. We present the MSE analysis of the proposed channel estimation based on the proposed pilot pattern and thoroughly investigate the MSE performance of channel estimation by a numerical method. A closed-form mathematical expression has been derived to express the MSE of the proposed channel estimation as a function of the Doppler shift, the number of resolvable paths of the channel, the polynomial order, and so on. Both computer simulation and numerical results show that the proposed channel estimation and data detection based on the proposed pilot pattern have effectively eliminated the ICI in terms of the MSE of the channel estimation and bit-error-rate (BER) performance, whereas the required pilot number per OFDM symbol is reduced by about 92.3% in comparison with that of using the grouped and equispaced pilot pattern.