This article reviews the detailed clinical and pathologic features of 278 cases of Warthin's tumor (cystadenolymphoma) from the files of the British Salivary Gland Tumor Panel. The tumor was found exclusively in the parotid gland, where it accounted for 14% of the total primary epithelial parotid tumors. The male predominance (1.6:1) was lower than in many earlier reports, and this observation is discussed. Some histopathologic features of both epithelium and stroma were semiquantified, and the presence of ciliated epithelium in a few tumors was confirmed. The Warthin's tumors were subclassified according to the scheme proposed by Seifert and colleagues. No examples of metaplastic Warthin's tumor were seen, but a few tumors were extensively necrotic and probably infarcted. The age distribution of patients with stroma-poor Warthin's tumor supported the concept that this variant develops by progressive adenomatous growth of typical Warthin's tumor. The histogenesis of Warthin's tumor is discussed briefly.