In this study, the results of open-wedge osteotomy with Puddu plate for the treatment of varus gonarthrosis have been evaluated prospectively. This study assessed 65 knees of 60 patients with varus gonarthrosis who underwent high tibial osteotomies. Our study population consisted of 13 male and 47 female patients with a mean age of 54 (range 39-76) years. For the clinical evaluation of the patients Hospital of Special Surgery (HSS) score, American Knee Society and Oxford knee scores, and for the radiological assessment mechanical axis deviation (MAD), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), femorotibial angle and Insall-Salvati index were basically taken into consideration. Our patients were followed up for an average of 34 (range 18-60) months. In the last assessments of our cases, mean improvements detected in HSS scores, Oxford knee scores, knee and functional scores of Knee Society were 26.72, 19.18, 49.9, and 30 points, respectively. The radiological examinations revealed that their mechanical axes on the average passed 5.09 mm laterally achieving an average of 6.5 degrees genu valgum, and a mean Insall-Salvati index of 1.09. As complications, superficial wound infection in two patients (3%), implant infections in one patient (1.5%), deep vein thrombosis in two patients (3%), peroperative lateral tibial plateau fracture in one patient (1.5%), and postoperative lateral tibial plateau fracture due to a falling down were encountered. According to the results obtained, postoperative pain resolves promptly and a significant degree of improvement of knee functions of the patients are achieved. Therefore, we believe that high tibial osteotomy with a Puddu plate is a valuable alternative to total knee arthroplasty in cases with varus gonarthrosis. Although early results are satisfactory, long-term follow-up studies are required especially in the middle aged and elderly patient populations.