Magnetic resonance imaging (MRI) was performed on 73 hips in 59 children aged 3 to 16 months after surgical reduction of developmental dislocation of the hip. Twenty-seven hips in 22 children had repeat MRI 6 weeks after reduction, and 20 hips in 16 patients had further MRI at least 1 year later. Only 38% of hips appeared concentrically reduced on the initial MRI scan, but this increased to 90% by 1 year later, without intervention. The authors measured coronal plane acetabular index and transverse plane anterior, posterior, and axial acetabular indices, as well as acetabular version and anteversion. Persistent difference could be shown in the coronal plane acetabular index between the dysplastic and normal sides for the cartilaginous anlage and the bony model of the acetabulum in scans performed at least 1 year after reduction. However, 40% of cartilaginous coronal plane acetabular indices fell within the "normal" range at 1 year. No other parameters could be shown to be persistently different.