By using the trellis approaches suggested by Wolf, block codes can be decoded by trellis decoding methods. The authors apply these methods to RS-convolutional concatenated codes and propose a decoding method using a single combined trellis structure comprising a convolutional code and RS code to easily obtain the soft decision decoding gain. The proposed decoding algorithm eliminates the need for a symbol interleaver, thus removing the time delay due to the symbol interleaver. The performance of the soft decision single trellis decoding of RS-convolutional concatenated codes over a fading channel is evaluated by simulation.