Matas'1 comprehensive study of primary thrombosis of the axillary vein makes it unnecessary for later writers to dwell at any length on the general aspects of the condition and goes far to answer his own criticism that the American literature is singularly barren of contributions to the subject. He is undoubtedly correct in his contention that even a casual survey of recent English and continental publications would increase to one hundred or perhaps more the number of cases (seventy-four) collected by Bruno Paggi in 1933. Nevertheless, the disease is unusual enough to warrant our recording two additional cases, neither of which belongs to the so-called "effort" group. We desire to report also certain studies which we have made on the living subject and on fresh autopsy material in an effort to unravel the still dubious etiology and which are not in accord with the theories heretofore advanced to explain