The authors analysed 150 consecutive cases of valgus osteotomy (Pauwels II) performed in cases of very severe osteoarthritis, and followed up for 3 to 10 years (average 6 years). The quality and the permanency of the results depend mainly on the morphology of the osteoarthritic hip. A satisfactory clinical and radiologic result is attained when the stresses in the joint have been reduced by improving the congruity of the joint surfaces using the cephalic medial osteophyte as part of these, and thus increasing the weight bearing surfaces. In osteoarthritis secondary to dysplasia (single dysplasia, subluxation, or luxation with support: 49 cases) valgus osteotomy gave 77 p. 100 good results, with 83 p. 100 painfree hips. This result persists 10 years (or more) for women operated before 50 years of age. The results are good in primary osteoarthritis occuring in active age (83 cases). When the hip was extruded by acetabular and cephalic osteophytes, 60 p. 100 good results, with 81 p. 100 painfree hips, have been obtained. In protrusive osteoarthritis and coxa profunda (18 cases) the valgus osteotomy slightly improved the range of movement but the relief of pain was usual (88 p. 100) and durable. The causes of failure (lack of mechanical improvement, osteoarthritis resulting more from biological disturbance--primary osteoarthritis--rather than from mechanical causes, influence of the age) have been sought for.