Sclerosing Sertoli cell tumor (SSCT) of the testis is rare, with only 22 previously reported cases. Most have been small, circumscribed masses, and none has had a malignant clinical course; however, follow-up is limited. We have examined 20 new SSCTs to better characterize their features and report long-term follow-up. At least focal tubule formation by sex cord cells in a dense, hypocellular fibrous stroma occupying at least 50% of the lesion was required. The patient age ranged from 23 to 52 years (mean, 37; median, 39). All SSCTs were unilateral with 11 left sided and 9 right sided. The average size was 1.7 cm (range, 0.5 to 6 cm). In most cases, the stroma represented 50% to 70% of the mass but was at least 80% in 2. The Sertoli cells formed cords, trabeculae, small nests, focal tubules (sometimes with a vague pseudovascular or retiform appearance), and rarely single cells. Most tumor cells had small, round, oval to polygonal nuclei with finely granular chromatin, small nucleoli, and modest amounts of pale, eosinophilic cytoplasm. No mitotic figures, significant atypia, or necrosis was seen. All tumors but 1 were circumscribed and lacked lymphovascular invasion. Follow-up in 15 patients (3 mo to 16 y; mean, 6.1 y) showed 9 alive and free of disease, 5 alive with unknown disease status, and 1 patient, who presented with bone metastases, dead of disease at 27 months. The only features in the malignant case that differed from all others in our study were lymphovascular invasion and lack of circumscription. Combining our cases with previously reported ones shows that SSCTs are unilateral, usually small (80% <2 cm) tumors that occur in a wide age range (18 to 80 y old; mean, 35 y) and lack necrosis. Only 1 of 31 with follow-up (mean, 4.4 y) metastasized; this tumor was 3.8 cm and had lymphovascular invasion and invasive growth. We conclude that SSCTs<2 cm with the typical features and lacking those associated with malignancy in Sertoli cell tumors, not otherwise specified, have a negligible risk of metastasis and are adequately managed by orchiectomy alone.