Objective: The main purposes of the present study were to analyse the long-term clinical and radiographic results of femoral varus derotation osteotomy performed in a group of patients with the diagnosis of Legg-Calvé-Perthes (LCP) disease and to compare the effects of age, lateral pillar classification, radiographic stage according to Waldenström’s classification, and the amount of varisation obtained on long-term results. Design: The study group consisted of 21 hips. The mean postoperative follow-up time was 25.1 years. The effect of age at the time of surgery, preoperative lateral pillar classification, Waldenström’s classification, and the amount of varisation on Merle d’Aubigne score, Stulberg class, and presence of degenerative arthritis of the hip joint were assessed at the final follow-up. Results: Better clinical and radiographic outcomes were detected in patients operated younger than 10 years. The hips with lateral pillar group C involvement preoperatively were found to be significantly associated with worse clinical scores, worse radiographic outcome, and higher rate of degenerative arthritis. The overall rate of the hips with good radiologic outcome was 52.4%. 7 hips had degenerative arthritis at the final follow-up. Conclusions: Femoral varus derotation osteotomy revealed a congruent joint in half of the operated hips and arthritis-free hip joint in 2/3 at 25 years follow-up. Age at the time of surgery and preoperative lateral pillar classification were the main determinants of the radiographic outcome whereas the factors significantly correlated with progression to degenerative arthritis were determined preoperative lateral pillar classification and Stulberg group at maturity.