This paper proposes a novel interference cancellation scheme that utilizes relay stations in multi-user transmission systems. Unlike conventional relay transmission schemes, the relay stations are used to decode the interference and transfer the pertinent information to the mobile stations. The proposed method takes advantage of the training signals and frame format of the interference at a neighboring cell when time division multiple access (TDMA) systems are applied. Even if external interference simultaneously arrives at the mobile stations during the transmission period from an access point to the mobile stations, the mobile stations employing the proposed scheme can effectively cancel the external interference because the relay station transfers the information related to the interference to the mobile stations. Moreover, we show that the proposed scheme improves the transmission efficiency compared to that for multi-user transmission without interference cancellation or with interference cancellation based on zero forcing algorithm when TDMA-based external interference is considered. (6 pages).