The Kimray-Greenfield venal caval filter is widely accepted as a means of preventing pulmonary embolism when medical anticoagulation has failed or complications have developed. When indicated, anticoagulants are usually resumed after placement of the filter. A retrospective study was performed comparing the thromboembolic and postphlebitic complications in patients who continued to receive anticoagulants after placement of the filter versus those who did not. Sixty-eight Kimray-Greenfield filters were placed in 68 patients (43 men and 25 women) during a four year period. After placement of the filter, 26 patients received anticoagulants and 42 did not. Three of those receiving anticoagulants and six of those who did not had significant swelling of the leg; two of those receiving anticoagulants and two of those who did not had a recurrent deep venous thrombosis. There were no instances of recurrent pulmonary embolism. There were no significant differences in the results of these two groups of patients. These results are consistent with those reported in the literature in that no correlation has been found between the use of anticoagulants after placement of the filter and recurrent thromboembolism or stasis sequelae. In view of the complications associated with medical anticoagulation, we recommend its discontinuation in all patients after placement of the Kimray-Greenfield filter.