Abstract: An optical system comprised of two cylindrically concave mirrors provides an advantageous rearward viewing device. Light rays from the object field to the rear proceed to a first mirror at the side of or above the observer, then to a second mirror forward of the observer, and then to the eyes of the observer. The mirror orientations and shapes are so determined as to produce cooperatively a suitably sharp, undistorted, and unreversed view to the rear over a usefully large angular extent. Comfortable binocular vision is obtainable along with latitude for movement of the observer's head. The system is particularly suited for use as a rearview periscope for vehicles. Examples of its use are given, along with procedures for determining the system designs which are applicable to a wide range of installation requirements.