Abstract: A device and method are disclosed for intravenous cannulation. The device employs a spring to precisely and accurately control the force and velocity imparted to a piercing needle, with mechanical constraints built into the device to precisely and accurately control the distance through which the piercing needle travels. A sheathed-needle configuration is used with an outer, echogenic needle that can be seen via ultrasound; and an inner needle used to pierce the vein. The operator releases the piercing needle with a controlled velocity, controlled force, and controlled travel distance. The device reduces the human error and complications that have previously been associated with manually piercing a vein for cannulation.