Although many studies have analyzed the success rates of closed reduction and spica casting for the treatment of developmental dysplasia of the hip (DDH) in children, the definition of success for this procedure is not standardized in the literature. We retrospectively reviewed our experience with closed reduction for treatment of DDH in 30 children (35 hips) over an 8-year period to determine the success rates of this procedure on the basis of how success is defined. In only 1 patient (2 hips, 6%) were the hips unable to be concentrically reduced with sufficient stability at the time of closed reduction. In 10 (30%) of the other 33 hips, the acetabulum failed to develop sufficiently after closed reduction, and a secondary surgery was required a mean of 22 months after cast removal. Four (12%) of the 33 hips developed radiographic evidence of avascular necrosis. Therefore, the success rate of closed reduction for DDH varies markedly depending on how success is defined.