Diagnostic and therapeutic indications have increased the need for ready access to the inferior vena cava. Multiple anomalies of the inferior vena cava have been described. Correct placement of a Greenfield filter in a left-sided vena cava requires recognition of this anomaly. Placement through a right internal jugular vein is preferable; however, if this is not possible, the left femoral vein should be used. Because of the incidence of anomalous inferior vena cava, routine inferior venacavography is recommended when an intracaval device is to be placed.