Aims: Evaluation of the clinical and radiological results after primary surgical treatment of CDH in children with late discovered CDH. Methods: We have studied 64 hips of 58 patients (51 female and 7 male), who were between 18 months-8 years old with late discovered CDH. The study was made between 1991–2000. Teratological and neuromuscular cases were excluded. None of the patients have had previous treatment before admission in hospital. Preoperative radiographic evaluation of the cases was made based on the Tšnnis classiþcation system (12-gr.I, 26-gr.II, 19-gr.III, 7-gr.IV). Preliminary traction was used in 5 hips (4 patients). 8 of them were treated by open reduction, 18 by open reduction and pericapsular osteotomy of the ilium described by Pemberton, 38 by combined pelvic osteotomy (29 Pem-berton osteotomy, 9 Chiari osteotomy) and femoral derotation and/or varus osteotomy (with femoral shortening in 8 cases). Postoperatively, a plaster cast was applied for 6 weeks. Average follow-up period was 6.8 years. Results: The radiological results are based on Severin Classiþcation. We obtained in 77.5% of the cases excellent, good and satisfactory results. Using the clinical rating system of Fergusson and Howard, the results were good and satisfactory in 78.8 of the cases. Avascular necrosis occurred in 6 cases, being rated as group II and III according to the Kalamchi and Mac Ewen classiþcation system. Conclusions: In case of late discovered CDH, the results of conservative treatment are not satisfactory, the surgical treatment being recommended. Four years old or elder children can be treated safely with one stage operation consisting of open reduction, pelvic osteotomy with or without femoral derotation and varus osteotomy (with shortening if it is necessary).