We propose a novel method to estimate and track the 3D line of sight of a person based on 3-D computer vision techniques. Most of the existing nonintrusive gaze tracking methods share a common drawback: users have to perform certain experiments in calibrating the user-dependent parameters before using the gaze tracking systems. These parameters are functions of the radius of the cornea, the position of the pupil, the position of user's head, etc.. Our approach, in contrast, employs multiple cameras and multiple point light sources to estimate the light of sight without using any of the user-dependent parameters. As a consequence, the users can avoid the inconvenient calibration process which may produce possible calibration errors. Computer simulations have been performed to confirm the proposed method. 1. Introduction When we stare at a 3-D point, our oculomotor mechanism controls our eyes such that the image of the point appears at the fovea region of our eyes. The 3-D LoS (Line of..