Recently several contrast delivery systems for coronary angiography have been introduced to provide adequate artery opacification through small catheters, which are thought to facilitate patient comfort and reduce hemorrhagic/vascular complications. However, the safety profile of a specific system has not been fully examined. In this case report, we present patients who underwent angiography using a contrast delivery system and suffered from massive air embolism necessitating mechanical support. We discuss the potential mechanism and the prevention of this complication.