We studied 4 new cases of juxtaglomerular cell tumor and compared their morphologic and immunohistochemical features with 2 renal hemangiopericytomas and 5 cutaneous glomus tumors. The juxtaglomerular tumors were resected from 2 males and 2 females (mean age at diagnosis, 23 years). Three patients manifested with severe hypertension. Tumors ranged from 2.2 to 8.0 cm and were well circumscribed. The tumors consisted of solid sheets and nodules of variably sized tumor cells with round, oval, and spindled nuclei alternating with edematous microcystic foci. Nuclear atypia, present in all tumors, was a prominent feature in 2. Mitotic activity was not identified. All cases showed hemorrhage, numerous mast cells, and thick-walled blood vessels. Unusual features included coagulative tumor necrosis, a hemangiopericytoma-like vascular pattern, and hyalinized stroma. All tumors were immunoreactive for CD34 and actin. Ultrastructural analysis revealed the presence of rhomboid-shaped renin protogranules. Patients were treated by partial or radical nephrectomy and followed up for 14 to 48 months. There were no recurrences or metastases. The characteristic clinical and morphologic features of juxtaglomerular cell tumor permit distinction from renal hemangiopericytoma and other renal tumors.