The authors discuss the basic principles in the reduction of scoliotic curves using the Maguelone method devised by Perdriolle and Vidal. The mechanical concepts of this method derive from corrective forces characteristic of the E.D.F. method but are used differently in terms of direction and quantitative relationships, namely derotation-de-flexion-kyphotisation replaces the elongation-de-flexion-derotation which characterizes the E.D.F. method. This modification is based on the assumption that in the pathogenesis of scoliosis the stages involve rotation, flexion and lordosis in that order. The method is discussed in detail as are the principles on which it is based. Finally, a group of cases are presented demonstrating the percentage gain after reduction, expressed in Cobb angles and degrees of torsion. The results appear to provide significant support for the effectiveness of the method.