Ten cases of femoral neck retroversions are reported in order to eliminate functional retroversions more frequent. True retroversions were confirmed by X-rays or by body scan which gives the exact degree of the retroversion. The authors emphasize the late onset, over eight, the first sign is lateral rotation of the gait and often a genu valgum. The imbalance between lateral and medial rotation is very important, the latter being very restricted. These retroversions are divided unanatomical forms which are mild and geometrical forms which are severe. These ones require surgical treatment which is derotation osteotomy of the femur.