Monocrystal anatase titanium dioxide (a-TiO2) films have been deposited on epi-GaN (0001)/sapphire substrates by the metalorganic chemical vapor deposition (MOCVD) method with the substrate temperature varied from 550 to 700 A degrees C. The structural analyses showed that the film deposited at 650 A degrees C was pure a-TiO2 monocrystal with the best crystalline quality. The epitaxial relationship between the film and GaN epilayer was determined as a-TiO2 (001)aEuro-GaN (0001) with a-TiO2 [110]aEuro-GaN aOE (c)>. The elemental composition and proportion were studied by the X-ray photoelectron spectroscopy (XPS) method, which proved the deposited film approximated stoichiometric TiO2. The films showed excellent transparency of similar to 90 % in the visible range with an optical band gap of 3.33 eV obtained for the 650 A degrees C-deposited sample.