PURPOSE: Vena cava syndrome (VCS) from stenosis of the superior vena cava or inferior vena cava caused by compression from a malignant tumor is one of the typical clinical conditions in patients with advanced stage malignant disease. VCS is difficult to manage and painful, reducing patients' quality of life. Although several reports have investigated stent placement for VCS, this treatment has never been established as the standard because of the lack of evidence of the safety and efficacy. We conducted a phase II trial and a phase III randomized controlled trial to clarify the role of stent placement in managing patients with VCS. METHODS: In the phase II trial, 28 eligible patients were treated with stent placement. The efficacy of stent placement for VCS was evaluated based on the reduction of patients' symptom scores during 14 days following treatment. Technical success, technical feasibility, overall survival, recurrence of symptoms, and adverse events were evaluated. In the phase III trial, 32 patients were enrolled and randomly assigned to the test (n = 16) and control groups (n = 16). The area under the symptom score curve was compared between the groups. The EQ-5D, SF-8, and adverse events were evaluated until discontinuation of the protocol treatment or 28 days after enrollment. RESULTS: In the phase II trial, the median patients' symptom scores significantly decreased from 10.50 before the procedure to 3.00 after the procedure. Technical success and technical feasibility rates were 96.4% and 100%, respectively. The incidence of treatment-related grade 3 or higher adverse events was 14.3%. In the phase III trial, significant superiority of stent placement was observed in the test, compared to that in the control, group. There was no significant difference in most other evaluations between the groups. CONCLUSIONS: Stent placement significantly improved the symptoms of VCS; thus, it might be accepted as the standard treatment to manage the symptoms of VCS. TRIAL REGISTRATION: JIVROSG-0402, JIVROSG-0807.