We have observed 74 cases of thymoma from 1968 to 1974. Six cases of invasive (malignant) thymoma presented in an unusual fashion with signs and symptoms of cardiovascular disease and superior vena caval syndrome. The clinical, pathological, and roentgenographic features of these cases are presented. The literature concerning cardiovascular involvement by thymoma is reviewed and discussed. Copyright © 1977 Wiley‐Liss, Inc., A Wiley Company