In flexible flatfeet in children the transition from physiological to pathological is obscure. This is seldom the case in pediatric foot deformities and makes assessment of the therapy required all the more difficult. On the other hand, the results of follow-up examinations of treated and non-treated cases of flexible flatfeet suggest that the value of arch-support insoles, which used to be prescribed widely, is more than questionable. In addition to the usual age-related fall of the medial arch and the physiologically accentuated valgus position of the calcaneous in children of preschool age, free movement of the joints of the foot should be taken into consideration in examinations, and attention should be paid to active correction of flexible flatfeet, in the tiptoe position. On the basis of our present knowledge, therapy only appears to be necessary for severe flexible flatfeet, i.e., when the heel valgus is over 20 degrees and, at the same time, there is complete lack of a medial arch. When weight is placed on the insole, the lack of medial arch can be seem to be completely or even convexly twisted. In cases of severe flexible flatfeet, further diagnostic clarification is usually necessary, in particular roentgenological examinations in order to exclude the possibility of other foot deformities by means of differential diagnosis.