A single-antenna interference cancellation-capable data detector employing the SAGE-algorithm for GSM downlink transmission with co-channel interference has been designed and tested. Two scenarios were considered: First, a frequency-flat Rayleigh fading scenario with synchronously received users. After analyzing this scenario, the data detector was extended to cope with an asynchronous multipath scenario. For reference purposes a conventional single-user detector as well as the optimal multiuser detector were designed and implemented. Simulations were conducted to assess the performance of the designed data detectors. The SAGE detector performs significantly better than the conventional single-user detector under influence of co-channel interference.