Primary renal lymphoma is very rare. The prognosis is usually poor with median survival less than a year. We report a case in a 55-year old man with a mass in the left kidney detected by ultrasonography and computed tomography. Radical nephrectomy was performed under a preliminary diagnosis of renal cell carcinoma. After the surgery, four courses of chemotherapy were performed. Prognosis may have improved since those reports in the earlier medical literature.