Of 29 reviewed ultrastructural studies of adenoid cystic carcinoma, only 1 mentions the presence of annulate lamellae. The present report describes a 65-year-old woman who presented with an adenoid cystic carcinoma in her left maxillary sinus. At the light microscopic level, most of the connective tissue was loose and myxomatous and contained fine strands, cords, and islands of epithelium that in places had a cribriform pattern. The ultrastructural appearance was similar to that described by others. Two epithelial cell types predominated. The cytoplasm of one type contained mainly ribosomes, and that of the other type also had peripheral microfilaments. Also present were pseudocysts, lumina with microvilli, and replicated basal lamina. In addition, a number of both types of cells contained parallel arrays of cisternae that had regular small pores. These were annulate lamellae.