Ischemic necrosis of the femoral head occurring after the treatment of congenital dysplasia of the hip can negatively affect the long-term prognosis of the involved hip. Some investigators have suggested that the presence of the ossific nucleus of the femoral head at the time of closed or open reduction is associated with a lower rate of ischemic necrosis. This finding, if verified, could lead to a delay in the treatment of a dislocated hip until ossification of the femoral head has begun, which may be well after the age when the patient has started to walk.We conducted a computerized search of the medical records at our two tertiary-care children's hospitals to identify all patients with congenital dysplasia of the hip who had had a closed or open reduction between January 1, 1979, and December 31, 1993. One hundred and twenty-four patients (153 hips) who satisfied the criteria for inclusion were identified. The ossific nucleus was present in ninety hips and absent in sixty-three. Closed reduction was used in 112 hips and open reduction, in forty-one. Ischemic necrosis was identified in five hips (3 percent): four (6 percent) of the sixty-three hips that did not have an ossific nucleus and one (1 percent) of the ninety hips that had an ossific nucleus at the time of the reduction. With the numbers available for study, we could not detect a difference between these two groups. The age at reduction (p > 0.99), the method of reduction (p = 0.611), previous treatment with a Pavlik harness (p = 0.592), the use of preliminary traction (p = 0.602), concomitant procedures (p > 0.99), and a failure of the primary closed reduction (p = 0.579) were not associated with the development of ischemic necrosis after reduction.In our analysis of patients who were managed over a fifteen-year period, the data did not support the hypothesis that the presence of an ossific nucleus at the time of reduction of a congenitally dislocated hip is associated with a lower prevalence of ischemic necrosis of the femoral head. Sound operative principles dictate that operative reduction of a congenitally displaced hip should be performed when the child can be safely placed under anesthesia and without regard to the presence or absence of the ossific nucleus.