Sinonasal seromucous adenocarcinomas may originate from the surface epithelium or from the submucosal glands. We reviewed the clinicopathologic material from 12 patients with sinonasal tract seromucous adenocarcinomas at the University of Texas M. D. Anderson Cancer Center (Houston, TX). There were nine men and three women age 30 to 87 years (mean age, 56.3 years). The clinical presentation included nasal obstruction, nasal mass, and epistaxis. Eight tumors were located in the nasal cavity, three in the ethmoidal sinuses, and one involved the nasal cavity and ethmoid. Histologically, in nine cases the neoplastic glands were lined by a single cell type, arranged back to back without intervening stroma and often inducing desmoplastic reaction. The remaining three tumors also had a cribriform and papillary pattern. All patients were treated by surgical resection. Three patients had recurrences, which occurred at 36, 36, and 48 months after initial therapy. Their treatment involved surgery and irradiation. Eleven patients are alive and free of disease at 36 to 108 months after diagnosis. One patient died 48 months after diagnosis of another cause. Sinonasal tract seromucous adenocarcinomas arise purely from submucosal seromucous glands. The diagnosis is facilitated by their anatomic location, the absence of tumor within the mucosal surface epithelium, and the striking similarity to terminal tubules of the seromucous glands.