Children possess certain physiological and anatomic characteristics that have traditionally been considered to impair thermoregulatory responses to exercise in the heat: low exercise economy, high ratio of body surface area to mass, diminished sweating capacity, and less cardiac output at the same work load compared with adults. Consequently, children have been regarded as an at-risk group for not only decrements of physical performance but also heat injury during physical activities performed in conditions of high ambient temperature. Recent investigations that have directly compared thermoregulatory responses to exercise in the heat in children and adults have challenged these traditional concepts. Such studies have failed to indicate group differences in heat dispersal when adult-child comparisons are appropriately considered in respect to relative exercise intensity. These findings imply that no maturational differences exist in thermal balance or endurance performance during exercise in the heat, nor that child athletes are more vulnerable to heat injury.