Abstract: An access system and method for obtaining access to the interior vascular structures or other regions or collections of fluid or fluid-filled cavities inside the body. The system and method provides for injection of contrast agents (to confirm ideal position or condition), the passage of guide wires, and the eventual catheterization of the heart and other parts of the body via the pathway established through the puncture of a femoral artery. The system and method provides the ability to inject a contrast material and pass a guide wire through the same introducer device simultaneously (without necessarily moving it or removing any parts), with the device designed to prevent the backflow of the contrast material through the guide wire port during the contrast injection process The ideal location of access in the vein or artery can be seen by injecting contrast from a needle inside the structure and then using fluoroscopy.