We followed up 34 secondary osteoarthritis patients with 38 hips treated by valgus-flexion osteotomy between 1979 and 1985. The average age of the patients at surgery was 45 years and the follow-up period ranged from 5 to 11 years. After surgery, the clinical evaluations were made according to the JOA Hip Score which remained unchanged in all 38 hips for 5 years. After 6 years there were some hips whose score declined with time. It was found that the preoperative extension-flexion range was the factor that was most closely associated with the result of the surgery (p less than 0.01). Radiological examination at 5 years revealed that the joint space had been widely broadened and the trabecular structure nearly normalized in 23 hips (60.5%), while 15 hips (39.5%) showed a slight degree of joint space broadening and were left with sclerosis and pseudocysts. After a lapse of 10 years or more, in 13 hips out of 10 patients, seven were found to have osteoarthritic changes and revision had to be done by THR in 2 patients. Valgus-flexion osteotomy can therefore be said to provide one of the useful means to preserve joints when employed in middle-aged patients with secondary OA.