The cytogenetic findings in 13 cultured Warthin's tumors (papillary cystadenoma lymphomatosum) are reported. Only one case showed an abnormal stemline. This was pseudodiploid and characterized by three different reciprocal translocations and one deletion. Small abnormal sidelines, however, were seen in three additional cases. All except one of the 12 tumors with a normal stemline contained variant cells. These showed a variety of numerical and/or structural aberrations. From this study it is obvious that to determine whether or not cytogenetically distinctive subgroups actually exist in cystadenolymphomas (as in pleomorphic adenomas) the number of cases must be greatly amplified.