A reduced-state sequence estimation (RSSE) for detecting orthogonal frequency division multiplexing (OFDM) signals transmitted over frequency selective Rayleigh fading channels is proposed. The Viterbi algorithm (VA) is used to search for the best path through the reduced-state trellis. Simulation results show that the proposed scheme reveals improved performance in symbol error rate (SER) compared to the previous noncoherent differential detection (NDD) methods.