Films containing thallium(III) oxide were grown by organometallic chemical vapor deposition in an oxygen-rich atmosphere on MgO, Al2O3, and Si substrates. Three organothallium precursors were used: thallium acetylacetonate, dimethylthallium acetylacetonate, and cyclopentadienylthallium. Films were characterized by using X-ray diffraction techniques and X-ray photoelectron, Auger electron, and infrared spectroscopies. The results indicate the presence of Tl2O3 as the major component with possible smaller amounts of Tl2CO3. Deposition on Si resulted in the formation of a silicate from interaction between the film and the substrate.