Warthin's tumor or papillary cystadenoma lymphomatosum (PCL) represents a clinically significant entity, not because of pernicious behavior, but because its cytohistological characteristics tell us much about the development and morphology of the parotid region. Three cases operated on in which PCL developed in an extraglandular location from the parotid, formed the basis for a series of observations on what is known about: 1. etiology of PCL; 2. the nature of the lymphocytic components; 3. the relatively high incidence of bilateral and multiple occurrence, as well as male predominance. These studies employed immunohistological techniques using a series of monoclonal antibodies.