OBJECTIVE:To investigate differences in performance between people with multiple sclerosis (MS) and control subjects on clinical tests of balance, and to assess performance consistency on balance tests in people with MS from morning to afternoon. STUDY DESIGN:Two factor repeated measures design with a two group sample of convenience. SETTING:Kingston Centre and the Camberwell Centre of the MS Society of Victoria, Australia. SUBJECTS:Fourteen people with MS and 14 control subjects matched for age, height, and sex. MAIN OUTCOME MEASURES:Subjects were measured on their ability to maintain standing balance in steady stance, (feet apart, feet together, stride stance, tandem stance, and single leg stance), during self-generated perturbations (functional reach, arm raise, and step tests) and in response to an external perturbation. Participants with MS were also asked to rate their fatigue level in the morning and afternoon. RESULTS:There were no differences between MS and control groups on the ability to maintain standing balance with feet apart, feet together, or in stride stance. Participants with MS performed more poorly than control subjects in tandem stance and single leg stance and in the functional reach test, arm raise test, step test, and in response to an external perturbation. There was little change in balance from morning to afternoon in participants with MS (ICCs (2,1) .70 to .94), despite an increase in self-rated fatigue (t(14) = -3.14, p = .008). CONCLUSION:The ability to maintain balance in standing is a marked problem in people with MS despite the consistency of their performance from morning to afternoon.