There is an urgent need for monographs on thrombosis and embolism since the subject has widespread interest. The methods of early diagnosis have been stressed in this treatise and the merits of conservative, anticoagulant and surgical therapy have been compared. The "do nothing" method of treatment is rightly condemned and a large number of case histories is presented to illustrate the value of exploring the common femoral vein and thoroughly aspirating and cleaning out the iliofemoral segment from the vena cava to the inguinal ligament. This procedure is then followed by heparinization. The author has devised a method of intramuscular administration of heparin with a concentrated solution, which requires from two to three injections in twenty-four hours and which he believes is suitable for home treatment. While such a method is obviously desirable and requires further exploration, it is certainly not ready for general use by the practitioner.