Thin film ferroelectrics are being developed for guided wave optical devices. Of particular interest is BaTiO3 because of its high electro-optic coefficient. Epitaxial thin films have been deposited by metalorganic chemical vapor deposition that are suitable for electro-optic devices. Thin film electro-optic modulators have been fabricated and their optical properties characterized. Factors that determine the ultimate bandwidth of these devices are discussed.