M. D. Anderson Hospital cases diagnosed as adenocarcinoma of minor salivary glands before 1977 were reviewed. Within this heterogeneous group of neoplasms there was identified one clinicopathologic tumor entity, which we have designated "polymorphous low-grade adenocarcinoma." The 14 tumors in that category were characterized by cytologic uniformity and histologic diversity; growth patterns varied (both within and among cases) from solid to tubular to papillary to cribriform (pseudoadenoid cystic) to fascicular, while the cells were always small to medium-sized, regular, and lacking in nuclear atypia. Mitotic figures were infrequent, and tumor necrosis was seen in only one instance (a recurrent neoplasm). Clear cytoplasm, oxyphilic and mucinous metaplasia, and intratubular calcification were sometimes present, and stromal mucinization and hyalinization were common. The tumors were always unencapsulated, and exhibited extension into surrounding tissues including bone. The 14 patients ranged in age from 27 to 76 years (median, 64 years). Eight were male and six were female; eight were white and six were black. The neoplasm was intraoral in all cases, involving the palate in 11, the buccal mucosa in two, and the posterior mandibular area in one. Local recurrence developed in one case, cervical lymph node metastasis in one, and both recurrence and cervical lymph node metastasis in two. The number of successive recurrences ranged up to three, and the interval to recurrence varied up to nine years (the interval to metastasis up to five years). Although radical surgical procedures were necessary for tumor control in some cases, no distant metastases occurred and all patients were clinically tumor-free at latest follow-up.