Renal transplantation is a unique renal replacement therapy because it is the most physiologic form of treatment in end stage renal failure. Case report: A 37 yrs old male with End stage renal failure due to hypertension on regular hemodialysis undergone kidney transplantation from living unrelated donor. His immunosupresive regimen was cyclosporine, azathioprine and prednisolon. He was discharged 2 weeks after operation with good condition and his serum creatinin was 1.4mg/dl. 3 months after transplantation he returned to hospital with muscle weakness and reduced urine volume. He was afebrile. His muscle forces were reduced. His serum creatinin was 3mg/dL. His muscle enzymes were increased several hundred time. Because of oliguria and hyperkalemia dialysis was begun and metylprednisolone pulse was administered intravenously, Azathioprine was replaced by mycophenolate mofetil. His EMG study showed neuromyogenic changes as in myopathy and his muscle biopsy revealed focal fiber necrosis, regenerating fibers and interstitial mononuclear cells infiltration as in inflammatory myopathy. The patient did not receive any drugs which can induce myopathy or myositis. FANA, Anti-dsDNA and ANCA,CMV Ab, HBsAg, HCVAb and HIVAb were negative . Complement level was normal. ESR was 73mm/hr. IVIG was administered. The patient`s muscle weakness was advanced leading to respiratory failure and was unfortunately died. In conclusion, since both polymyositis was not reported as renal transplantation and also tests of other causes of polymyositis were negative therefore we suggest this is a rare case of solid organ transplantation or a rare condition of coincidence of two unrelated diseases.