Eighty-five patients were surgically treated for postmastectomy edema of the upper extremity. In 20 of them, phlebolysis of the subclavian vein was performed. It was established that the vein was most often compressed by a long stump of the small pectoral muscle. Surgery and subsequent radiation treatment create unfavorable conditions for the muscle leading to its morphologic restructuring. Classic mastectomy after Halsted-Meier is recommended.