Hip rotation in extension and flexion was studied in 23 patients with idiopathic intoeing gait. In extension all the hips had markedly increased medial rotation and limited lateral rotation, fulfilling the criteria of excessive femoral anteversion. In flexion, however, rotation varied widely; in one group of patients medial rotation remained greater than lateral, but in the second group lateral rotation was equal to or greater than medial. CT scans showed that the hips in the first group were significantly more anteverted than those in the second. Clearly measurement of hip rotation in extension alone does not provide a dependable indication of femoral anteversion in children with intoeing gait; rotation in flexion also needs to be measured.