Drawing upon a total experience of 450 hips affected by established congenital dislocation or subluxation, the author presents the long-term results in 177 hips treated for the first time between the ages of nine months and three and a half years, in support of his contention that surgical endeavour should in the first place be directed towards the limbus and upper end of femur rather than the acetabulum. The 144 patients, all treated on lines previously described in this journal (Scott 1953; Somerville 1953a, b; Somerville and Scott 1957), have now been followed up annually for between ten and twenty-five years, both hips receiving equal scrutiny. In brief, the routine has consisted of arthrography, excision of any limbus shown to be inverted, reduction by traction in abduction, and rotation osteotomy of 70 degrees. The addition of 10 to 15 degrees of varus was found beneficial and has become routine. Some hips required secondary procedures, and regret is expressed that these were not carried out sooner. The upper age at which recovery of the acetabulum may occur was found to be much higher than generally supposed, with a critical period between eleven and fourteen. The main conclusion is that in the great majority of cases first seen in this particular age group, improvement of the mechanics of the joint, especially by attention to the upper end of femur, leads to satisfactory development of the acetabulum and good functional results, at least up to early adult life.