The primary objective of this project is to track changes over time in balance control parameters measured during stance and gait for different groups of multiple sclerosis (MS) patients. Our primary goal is to determine whether these changes in balance control over time predict transitions in MS progression to a more disease affected state, and are different from changes over time for patients with balance deficits due to vestibular sensory disorders. A part of this goal is also to determine whether these changes in balance control are correlated with changes in patients' self-reported deficits and are similar to those changes in balance control of patients with peripheral vestibular loss. The secondary objective is to determine for multiple sclerosis (MS) patients the relationship of their balance parameters to different gait speeds, in order to advise them on, and promote via feedback, safe walking speeds. Fulfilling the first of our objectives would lead to better tracking of MS disease changes over time, earlier quantification of onset of symptoms suggesting a worsening of disease status, and, we assume, greater patient satisfaction knowing that quantification of symptoms fits subjective feelings of balance deficits during stance and gait. Achieving the second objective would lead to improved balance during gait. We aim to carry out these objectives using equipment (SwayStar) which we have proven is sensitive to MS induced balance deficits {2}, but costs far less to operate and maintain than previously used quantification tools. We aim to investigate the balance deficits during gait in different MS patient groups using a multimodal approach with a SwayStar system (analysis of balance during stance and gait in terms of trunk-pelvis movements near the centre of mass) and patient questionnaires.