Previous clinical studies have studied tibiofibular torsion by measuring the angular difference between a proximal (often bicondylar) plane and a distal bimalleolar plane. We measured the angular difference between the proximal and distal posterior tibial planes as defined by ultrasound scans. We found no significant torsional difference between the right and left tibiae of 87 normal children, nor between their different age groups. The mean external torsion of 58 legs with congenital talipes equinovarus was 18 degrees; significantly less than the mean 40 degrees in the normal children and 27 degrees in the clinically normal legs of the 22 patients with unilateral congenital talipes equinovarus. We did not confirm the previously reported increase in external torsion with increasing age. The relative internal tibial torsion we have demonstrated in patients with congenital talipes equinovarus must be differentiated from the posterior displacement of the distal fibula observed by others and which may result from manipulative treatment. The relative internal tibial torsion we found in the clinically normal legs of children with congenital talipes equinovarus is further evidence that in this condition the pathology is not confined to the clinically affected foot.