Abstract: This invention pertains to blood vessel cannulation devices and methods for sensing the location of a blood vessel, for cannulation with precision and ease. In preferred embodiments, the blood vessel cannulation device preferably comprises a mounting assembly for securing the device to a patient in the vicinity of a blood vessel. A rotating assembly is mounted to the mounting assembly for rotation with respect to the mounting assembly. A guide housing is mounted to the rotating assembly for traverse across the rotating assembly, and for rotating with the rotating assembly. Sensor guides in the guide housing receive one or more sensors which sense the blood vessel. Rotating the rotating assembly, and traversing the guide housing, enable bringing the bottom ends of the sensor guides into alignment with the blood vessel, correspondingly also bringing a cannula guide, also present in the guide housing, into alignment with the blood vessel.