The purpose of this investigation was to study the effect of elevating the heel during unilateral weight-bearing on structure of the foot, especially a "flat" foot, and on function of the foot in maintaining balance. We examined 16 healthy women, 21 to 23 years of age, who stood unilaterally on the right foot with the heel elevated 0, 5, 10, 15, 20, 25, 30, and 40 mm. We measured height of the medial longitudinal arch, rearfoot pronation (calf-to-calcaneus angle), displacement of center of pressure under the foot during ten seconds, and mean position of the center of pressure during those ten seconds. Elevating the heel raised the medial longitudinal arch, reduced rearfoot pronation, increased length of displacement of the center of pressure, and brought the mean center of pressure forward and medially. In feet that initially had strong rearfoot pronation, presence of an initially high medial longitudinal arch was associated with a greater curtailment of rearfoot pronation when the heel was elevated than if the arch was not initially high. These results suggest that elevating the heel of a shoe can help reduce the signs of a flat foot, but the accompanying decrease in balance stability and shift of pressure toward the first metatarsal head makes the use of elevated heels questionable as a therapeutic measure.