A case of Sertoli cell tumor of the testicle is reported. A 33-year-old man visited the Chiba University Hospital with the chief complaint of a painless right testicular swelling on May 1990. The right testis was hard and swollen on palpation. Gynecomastia was not present. Serum levels of tumor markers and hormones including alphafetoprotein, human chorionic gonadotropin-beta, carcinoembryonic antigen, testosterone, prolactin, estradiol, luteinizing hormone, and follicle stimulating hormone were within normal limits. Ultrasonic examination showed a high echoic lesion in the right testis. Computerized tomography and magnetic resonance imaging showed no evidence of retroperitoneal lymph node enlargement. A high right orchiectomy was performed under a diagnosis of right testicular tumor. The right testis was elastic hard and measured 9 x 10 x 7 cm, weighing 450 g. The cut surface was light yellowish white and was completely displaced by the tumor. No normal tissue was seen. Histological examination showed a Sertoli cell tumor. No adjuvant therapy was performed. Neither recurrence nor evidence of metastasis has been detected for 8 years postoperatively.