This paper presents field trial results for downlink interference cancellation in a live GSM network. Uplink interference cancellation techniques have been developed in the past, which exploit the use of multiple receive antennas. However, downlink techniques are typically limited to just the use of a single receive antenna due to space limitations, cost considerations and aesthetics associated with current mobile station designs. A prototype mobile station, using a low complexity single antenna interference cancellation (SAIC) algorithm, was constructed, and used to assess the network gain in both asynchronous and synchronous GSM networks. The performance results measured show that SAIC techniques can provide significant gains in C/I. In addition, network simulations indicate that this same algorithm can support voice capacity gains of 39-57%. Thus, SAIC is seen to be a very viable technology for GSM capacity improvement, which can be realized in the next generation of mobile stations.