Introduction: Limb-salvage surgery has become the standard mode for treatment of the proximal tibia tumors. Its goals are complete eradication of the tumor with minimal complications, while maintaining acceptable functional, durability and cosmetic appearance of the limb. The most serious problem encountered after tumor resection and skeletal reconstruction by endoprosthesis or bone grafts is the lack of enough soft tissue coverage, which is the direct cause of delayed wound healing, exposure of prosthesis and infection. Another difficult aspect is the need for reconstruction of the extirpated extensor mechanism. In the present study the medial head gastrocnemius muscle flap was used to reconstruct the defect, cover the prosthesis and / or the fibular graft, as well as to reconstruct the extensor mechanism. Both the clinical outcome and functional results will be presented. Patients and methods: Sixteen patients (8 males and 8 females), with a mean age of 24.4 years (range 13-58 years) at time of surgery, were included in this work. According to the staging system of Enneking et al, they were 4 patients with an aggressive giant cell tumor (25%), and 12 patients with primary malignant bone tumors (75%) of the proximal tibia. One of the 12 patients was grade I B and the other 11 were grade II B. Wide resection was performed in all the patients followed by reconstruction by modular replacement endoprosthetic system in 10 patients, pedicled fibular transfer and knee fusion in three patients, and non-vascularized fibula graft with knee fusion in three patients. In all the 16 patients a medial head gastrocnemius transposition muscle flap was used for coverage and to reconstruct the extensor mechanism. The   follow   up   ranged   from   6   to   108   months   with   a   mean   of   67.6   months. Results: The overall survival rate at the last follow up was 81.25% (13 patients), three patients (18.75%) died at 6, 10, 16 months postoperative from distant metastasis. Fourteen of the 16 gastrocnemius muscle flaps survived without complications. In 2 patients, infection developed three weeks after surgery. In one patient the infection subsided after multiple measures, while in the second, amputation was performed to save patient's life. The mean Musculoskeletal Tumor Society Score at follow-up was 81.2% (range, 74-90%) and the mean range of motion was satisfactory with only extension lag 5-15 degrees in the ten patients with prosthetic replacement. Conclusion: The use of the medial head gastrocnemius muscle flap after wide excision and skeletal reconstruction of aggressive proximal tibia tumors provides successful soft tissue coverage and durable reconstruction of the extensor mechanism with satisfactory functional outcome. It is technically easy, safe and reliable, with a high survival rate and with minimal donor site morbidity if any. The well-vascularized muscle flap can combat wound infection and minimize wound dehiscence