Imaging findings are presented of an unusual pathway of collateral circulation consisting of bilateral and diffuse dilated breast veins from a patient with long standing superior vena caval syndrome. The main importance of this case is the extent of the collateral development through the breast veins, serving as the major pathway of collateral circulation. Identification of this unusual collateral development. which resembles breast varices, was performed with contrast-enhanced chest CT scans, digital subtraction venography, color Doppler ultrasonography, and mammographic studies. Collateral development was secondary to a long segment idiopathic venous occlusion involving bilateral subclavian and brachiocephalic veins as well as vena cava superior. We conclude that dilated breast veins when detected on any imaging modality should raise the suspicion of central venous obstruction. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.