Rotational problems of the lower extremity affect a vast number of infants and children. Like flexible flat feet, bowed legs, and genu valgum, rotational problems fall into the category of physiological or postural problems that occur in normal infants and children. Some deformities, such as metatarsus adductus, are secondary to intrauterine position. Most problems, such as medial tibial torsion, represent a variability during a stage of normal development, whereas problems such as medial femoral torsion are often inherited. Rarely, these problems persist into adolescence and, if they are severe, they can result in disability. Rotational problems of the lower extremity in infants and children often concern parents enough to prompt them to seek a consultation with an orthopaedic surgeon. Optimum management is based on an understanding of the cause and natural history, of the condition and of the effectiveness of various treatment options. Management ranges from simple observation to shoe modifications, bracing, physical therapy, and operative treatment. In this lecture, I will make suggestions concerning management on the basis of objective data rather than on the basis of tradition or speculation. The normal range of rotation of the foot, leg, and hip was defined to include measurements that fall within two standard deviations of the mean. Rotation within the normal range is described as version; that outside the range of normal is described as torsion. For example. children normally have femoral anteversion. Those with hip rotation values that are outside the normal range are said to have medial or lateral femoral torsion.