Abstract: An ultrasound transducer is translatable for scanning along a body surface by having the transducer mounted at the free end of an articulated arm which is moved in a single nominally vertical plane during a scan. The arm is pivotally connected at one end to a head which is turnable at least about a vertical axis so the arm can be directed in other single planes. The head is mounted on a horizontally and transversely movable arm which is on a longitudinally movable carriage. Potentiometers produce analog signals which allow a microprocessor to determine the difference between the location of the transducer axis and the vertical axis about which the arm swings into different planes. When isocentric rotation is desired, the user locates the transducer over the isocentric point on the body and provides a command signal which, through a servo motor system, causes the transverse arm and longitudinal carriage to move until the vertical head axis is aligned with the transducer.