Abstract: This invention pertains to blood vessel cannulation devices and methods for sensing the location of a blood vessel. 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 mounted to the mounting assembly, and a guide housing mounted to the rotating assembly. Sensing 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 sensing guides into alignment with the blood vessel, correspondingly also bringing a cannula guide, in the guide housing, into alignment with the blood vessel. Cannulation, is improved by the alignment of the bottom end of the cannula guide with respective bottom ends of the sensing guides.