The authors present their experience with high tibial osteotomy for the correction of varus knee, performed wih an open wedge technique (Puddu). This technique allows correction of varus knee with a medial tibial osteotomy open wedge, using a special tibial plate; this plate is fixed with two cortical screws and two spongious screws and is formed by a tooth that prevents the correction from loosening. The aim of our work is the retrospective clinical and radiographic evaluation of 18 patients treated with Puddu technique at the University of Naples. Indications for this technique are: constitutional varus knee, chondral damage after medial meniscectomy and medial gonarthrosis. From June 1999 to the present we treated 18 patients (13 women, five men), median age 54, with high tibial osteotomy with Puddu technique at the department of Orthopaedics and Traumatology of the University of Naples. Before the osteotomy we normally perform a knee arthroscopy to achieve a correct articular balance (evaluation of articular cartilage, menisci and ligaments) and to treat associated lesions. All patients were evaluated by clinical examination with IKDC score and X-rays. Median follow-up was 30 months. Results are very good with an important improvement in pain and disability. Vascular and neurological complications were not found in any of the patients; all the osteotomies had a strong consolidation and showed good correction of the deformity. High tibial osteotomy with Puddu technique in our opinion seems to be an effective technique in the treatment of medial knee arthritis and in the correction of femoral-tibial axis. It is an easy, reproducible and trusted technique and in our opinion recommended over the traditional tibial osteotomies (closed wedge osteotomy, dome osteotomy and osteotomy with external fixation, etc).