Nowadays, partial nephrectomy is often selected for treatment of small renal cell carcinoma (RCC) because T1a RCC shows a favorable prognosis with a 5-year overall-survival rate exceeding 90%. To determine the methodological usefulness and treatment outcome of partial nephrectomy using microwave tissue coagulator (MTC), we evaluated our series of 121 patients (124 kidneys) with T1 RCC who underwent this procedure. Ninety-nine patients were elective and 22 patients were imperative cases. This procedure was indicated for asymptomatic solitary RCC; < or =4 cm in diameter in elective cases or < or =5 cm in imperative cases, expanding outward with a clear capsule, and showing neither renal pelvis nor renal sinus invasion. The median operation time was 150 minutes and the median blood loss was 217 ml. Eight patients needed transfusion, and conservative therapy cured 4 patients of postoperative urine leakage successfully. Three patients underwent early secondary nephrectomy due to multiple RCCs, invasive spindle cell carcinoma, or prolongation of urine leakage. No significant deterioration of renal function by creatinine clearance (Ccr) was observed, and postoperative Ccr could be precisely predicted from preoperative serum creatinine value and the renal parenchymal volume estimated with 3-dimensinal image reconstruction. Five-year overall-survival rate was 91% at the mean follow-up of up to 37.9 months and 107 patients were alive without disease. One patient showed local recurrence 2 years later and underwent radical nephrectomy. We believe that non-ischemic partial nephrectmy using MTC is a simple and reliable nephron-sparing surgery for small RCC in respect of postoperative recurrence and preservation of renal function.