Research on balance in the medio-lateral direction is sparse compared to that undertaken in the anterior-posterior direction. There is a correlation between poor medio-lateral balance and falls investigated in elderly and recently in subjects with hemiplegia. Investigations into the muscle activity required for medio-lateral balance in normal and hemiplegic subjects suggest falls may occur as a result of poor timing, modulation and duration of specific muscle activity essential for medio-lateral balance. Further, there is support for retraining medio-lateral balance using task related functional activities. The results of a single subject design experiment undertaken as part of this dissertation indicated that medio-lateral balance in a hemiplegic subject, can be retrained using body weight support treadmill training, two years after stroke. Results from this study therefore provide support for this physiotherapy technique being effective in improving medio-lateral balance in subjects with hemiplegia.