The incidence of pulmonary embolism is an indicator of the effectiveness of inferior vena cava filter (IVCF) insertion. The incidence of pulmonary embolism after IVCF placement is generally considered to be about 2% to 5%. Most pulmonary embolisms after filter placement are asymptomatic and difficult to diagnose. Therefore, the incidence of pulmonary embolism after filter placement is actually higher than this value. In a prospective, randomized study of 400 patients with deep vein thrombosis with (200) and without filter placement (200) and concomitant anticoagulation, the incidence of pulmonary embolism was four times higher in the no filter placement group than in the filter placement group at 12-day follow-up (4.8% in the no filter placement group and 1.1% in the filter placement group). The difference between the two groups was even more pronounced when comparing only patients with existing pulmonary embolism at enrollment (8.6% in the no filter group and 1.1% in the filter group). However, there was no significant difference in the rate of death between these two groups. In addition, the difference in the incidence of pulmonary embolism between the two groups was not statistically significant at the 2-year follow-up. However, a study with an 8-year follow-up showed that the incidence of symptomatic pulmonary embolism was significantly lower in the filter placement group compared with the no filter placement group (6.2% in the filter placement group compared with 15.1% in the no filter placement group). Although the indications for IVCF placement are still debated, it is well established that filters reduce the incidence of pulmonary embolism. The use of temporary and removable filters is recommended to minimize complications associated with prolonged filter placement. The use of filters should be chosen appropriately for different situations and purposes.