From September, 1983 to May, 1993, 137 hips of develomental dislocation of the hip(DDH) in the 125 patients have been admitted and treated at the Department of Orthopaedic Surgery, Guro Hospital, Korea University. Among them, the cases of bilateral DDH's, acetabuloplasty-performed cases were excluded and the remaining 66 cases which had been followed-up more than 2 years were analyzed from the point of view of developmental behavior of DDH's after reduction. 1. Among the 66 patients, 11 of them(16.7%) were male, and the rest(55, 83.3%) were female. There were 37 cases(59.0%) in right side, 29 cases(41.0%) in left side, and the average age at reduction was 2 year 7 months old(range: 3 months to 9 year 3 months old). 2. Treatments offerred were either closed reduction with adductor tenotomy(40 cases, 60.1%) or open reduction with femoral osteotomy(26 cases, 39.9%). 3. Age at reduction, change of acetabular index in pre- and post-reduction state, center-head distance discrepancy (CHDD, Kuo, 1994) based on the radiographs taken at 1 year after reduction were recorded and analyzed. 4. The younger groups which were reduced before the age of 18 months showed satisfactory result(Gibson & benson I, II) in 83.8%, wheres the older groups satisfactory in 31.0% 5. The groups of CHDD less than 6% revealed satisfactory result in 87.1%, and unsatisfactory result in 12.9%. The groups of CHDD more than 6% revealed satisfactory results in 31.4%, and unsatisfactory results in 68.6%. 6. This study seems suggestive of the fact that age at reduction, CHDD at postreduction 1 year state and decrement of acetabular index are some of the factors which are reliable in terms of prognostication of DDH after reduction.