CD43, a sialoglycoprotein expressed on hematopoietic cells, has only rarely been reported in nonhematopoietic tumors, mostly of colon. We describe CD43 expression by immunohistochemistry and mRNA in situ hybridization in adenoid cystic carcinomas (ACCs). CD43 immunoreactivity with 2 different antibodies was detected mainly in ACC but also 1 membranous type basal cell adenocarcinoma and 1 colonic adenocarcinoma. Nine of 20 (45%) ACC (8/17 salivary/mucoserous and 1/3 mammary) showed immunoreactivity with clone MT1 whereas 4 (23.5%) salivary ACC also showed immunoreactivity with clone DF-T1. The few high-grade, angioinvasive ACC in our study did not seem to express CD43. CD43 mRNA was detected by in situ hybridization in 2 of the 3 ACC that were CD43 positive on immunohistochemistry but not on any CD43 negative cases tested. Hence, CD43 seems to be selectively expressed in a subset of ACC and its significance in salivary tumors is discussed.