Adenoid cystic carcinoma (ACC) of salivary gland origin shows histologic patterns (tubular, cribriform, solid) that have been correlated with the clinical course of the disease. Recognition of tubular pattern is generally easy. Discrimination between cribriform and solid types leaves some margin for the pathologist's subjective interpretation because it is essentially based on the amount of gland-like spaces, containing mucinous or hyalinized material, which are present in neoplastic nests. To overcome this problem and with the aim of identifying a more objective basis for prognostic evaluation of cribriform and solid ACC, the authors counted the number of gland-like spaces per square millimeter of tumor, excluding supporting stroma and small areas with the tubular pattern, in a group of tumors similar with regard to therapy, stage of disease, and microscopic evidence of tumor-free surgical margins. According to the authors' data, the number of gland-like spaces per square millimeter of tumor appears to be a reliable and objective measure for prognostic evaluation of cribriform and solid pattern ACC; in particular, the greater the number of gland-like spaces per square millimeter of tumor, the longer the survival of the patient.