Stannic oxide in its pure form is an n‐type wide‐bandgap semiconductor. Its electrical conduction results from the existence of point defects (native and foreign atoms) which act as donors or acceptors. Some unique properties of make the material useful for many applications; therefore, increasing attention is being paid to studies on this oxide, especially on the methods of preparation, and its electrical and optical properties. The purpose of this series is to provide a general up‐to‐date review of the investigations carried out and to help identify important areas for further studies. The first part was concerned with the preparation and defect structure of single crystals, sintered polycrystalline samples, and thin films, and in the second part we reviewed the electrical properties of these materials. In this part we discuss the optical properties of single crystals and films. This concludes our review of the physical properties of materials.