Blount's disease is associated with agenesis of the medial tibial plateau leading to tibia vara. It appears to be more frequent in Scandinavian countries and in black populations. Twenty-six cases had been seen in Martinique (Antilles) of whom twenty were children. A classification into six stages was described. Stage IV is a critical one. Before it, corrective osteotomy will often lead to complete healing. After stage IV, lateral epiphysiodesis must be added to avoid recurrence of deformity. The technique of osteotomy was variable according to the age of the child and the obliquity of the joint line. In young children, a subtraction closing wedge osteotomy is suitable. In older children a "V" shaped osteotomy is recommended to lessen the amount of shortening. At the end of the growth period, a medial opening wedge osteotomy is advisable. In adults (six cases) whose deformity can reach as much as 50 degrees with considerable ligamentous laxity, reefing of the ligament must be added to the osteotomy. The problem of the opposite knee is discussed. Even when the disease is not bilateral, it can tend to develop towards arthrosis.