Nine cases identified as acinic cell adenocarcinoma of minor salivary glands from the files of the Armed Forces Institute of Pathology and the Department of Pathology, Temple University School of Dentistry were studied to determine the clinical and histomorphologic parameters of this lesion. One case was examined ultrastructurally. Clinical results show that the tumor is more common in females and the average age of patients was 42.5 years. The most common sites were upper and lower lips and buccal mucosa. The tumor tends to be locally limited, but recurrence is a distinct possibilty. Cytologic features usually associated with malignancies are generally not present. However, perineural space and muscle invasion occur, and it is felt that this tumor should be considered as a low-grade malignancy. Fine structural observations showed the presence of cells with serous secretory granules and cells with mucous globules. However, the serous secretory granules were not as numerous as those reported in the acinic cell adenocarcinoma of the parotid gland. It appears that these tumors arise from intercalated duct cells or pluripotential duct cells rather than from fully differentiated serous cells.