The frequency of thromboses or of obstacles to the venous flow in brachial or axillary regions has been examined by a phlebographic survey of 102 patients who were treated surgically and radiotherapeutically because of cancers of the breast. Thromboses or venous obstruction were found in the 86 patients with brachial edema. Ten of the patients with brachial edema had thromboses. Further 15 suffered from an obstruction to the venous flow. The results are discussed in detail, and compared with the rather contradictory data in literature. As a consequence of this study an indication for brachial phlebography would be justified on a larger scale with patients having been treated surgically because of mammary carcinoma.