Given a pair of stereo images, rectification determines a transformation of each image plane such that pairs of conjugate epipolar lines become collinear and parallel to one of the image axes. The rectified images can be thought of as acquired by a new stereo rig, obtained by rotating the original cameras around the optical centre. The important advantage of rectification is that computing correspondences, a 2-D search problem in general, is reduced to a 1-D search problem, typically along the horizontal raster lines of the rectified images. A good starting point to explore the literature on rectification includes [1, 5, 6, 8, 4, 9]. After reviewing some concepts related to the pinhole camera model and the epipolar geometry, we will discuss in detail the process of rectification.