Numerous trials have shown that physical activity and exercise training have beneficial effects in general older populations. However, few have studied its effectiveness among people with dementia. The aim of this systematic review is to examine the efficacy of trials using a rigorous randomised, controlled design and including physical activity or exercise as a major component of intervention on the physical functioning, mobility and functional limitations of people with dementia. We found 20 randomised controlled trials that included a total of 1378 participants. Of these, only three were of high methodological quality, and six of moderate quality. Nevertheless, these studies consistently show that intensive physical rehabilitation enhances mobility and, when administered over a long period, may also improve the physical functioning of patients with dementia.