Distal femoral varus osteotomy (DFVO) of the knee may be indicated for young, active patients with unicompartmental arthritis and valgus deformity. We report on 40 DFVOs with a mean follow-up of 123 months. At the most recent follow-up, 24 knees had good or excellent results (60%), 3 had fair results (7.5%), and 3 had poor results (7.5%). Four in the fair/poor group were awaiting total knee arthroplasty. Eight knees (20%) had been converted to total knee arthroplasty. Mean Knee Society objective score improved from 18 (range, 0-74) to 87.2 (range, 50-100). Mean Knee Society function score improved from 54 (range, 0-100) to 85.6 (range, 40-100). Ten-year survival rate of the DFVO was 82% (95% confidence interval, 75%-89%) and the 15-year survival rate was 45% (95% confidence interval, 33%-57%).