For the past 30 years patients presenting with the superior vena caval syndrome (SVCS) have, as a recommended practice, been treated with radiotherapy without necessarily establishing a tissue diagnosis. This practice has been pursued as it was accepted that the probability that unresectable lung cancer was the cause of the syndrome was high; that SVCS was a condition for which diagnostic procedures carried a high risk; and that SVCS was a life-threatening situation requiring immediate relief. To assess the validity of this practice, the literature since 1934 was reviewed. One thousand nine hundred eighty-six cases of reported SVCS were identified resulting in the emergence of several important facts: (1) small cell lung cancer is currently the leading etiology of SVCS accounting for approximately 40% of all cases due to lung cancer; (2) the experience with performing thoracotomies, mediastinoscopies, bronchoscopies, lymph node biopsies, and venograms as reported in the literature suggests that all of these diagnostic procedures can be performed safely; (3) while the SVCS can cause worrisome symptomatology, there is little reported clinical or experimental evidence that an unrelieved SVCS is life threatening; and (4) patency of the SVCS may not be reestablished after palliative therapy even though signs and symptoms may resolve. Because of therapeutic advances in the treatment of small cell lung cancer, lymphoproliferative disorders, and other malignant etiologies of the SVCS, the findings of this review suggest that a policy of treatment without histologic diagnosis is ill advised.