Two cases of downward migration of the Günther vena caval filter are reported. Migration resulted in recurrent pulmonary embolism in one case; in the second, partial thrombosis of the filter precluded retrieval. Both patients were treated successfully by placement of a second Günther filter in the infrarenal vena cava. Until more experience with this filter is available, the authors recommend use of the 30-mm filter in medium- and large-size venae cavae. Radiographs should be obtained to check the position of the filter immediately and 1 week after placement. In addition anticoagulative therapy should be continued whenever possible.