62 cases of adenoid cystic carcinoma (ACC) arising in major and minor salivary glaads were studied. Factors which appeared to influence the clinical course included: 1) histologic pattern, 2) presence or absence of tumor on the surgical lines of excision, 3) site, 4) size of primary lesion, 5 ) presence or absence of tumor in lymph nodes, and 6) degree of cellular atypia. On histologic examination, these neoplasms were classified according to their predominant histologic pattern (tubular, cribriform or solid). Recurrences have been seen in 59% of patients with ACC demonstrating a predominantly "tubular" pattern, as compared to 89% for the "cribriform" lesions and 100% for the "solid" neoplasms. Of patients who eventually died of tumor, those having "tubular" predominant lesions had the longest course (average 9 years before death, in contrast to 8 years for the "cribriform" and 5 years for the "solid" tumors). Our findings suggest that the "tubular" predominant pattern has the best prognosis and represents the best differentiated histologic form of ACC. In contrast, the "solid" pattern is the least differentiated and is associated with the worst prognosis. The predominantly "cribriform" lesions appear to lie between the other two forms both clinically and histologically.