The literature concerning ambulation of normal and disabled persons (amputees, hemiplegics and paraplegics) is reviewed, along with studies of the energy cost of ambulating with assistive devices and of wheelchair locomotion. According to an average of the results available from the literature, a normal person walks at about 83 m/min, with an energy expenditure (.ovrhdot.Ee) of 0.063 kcal/min per kg and 0.00764 kcal/m per kg. The disabled person walks more slowly, to avoid incurring an increase in .ovrhdot.Ee/minute. The more disabled the person, the more determinants of gait lost; thus, the more slowly he walks and the less efficient he becomes in terms of .ovrhdot.Ee/kcal per unit distance. The importance of a common terminology when measuring the energy cost of ambulation and the need to allow subjects to walk at their own most comfortable walking speed were stressed.