The authors report optical properties and interband-transition critical-point energies of bulk BaTiO3 (001). Room-temperature pseudodielectric function spectrum =+i from 1.5 to 5.2 eV has been measured by spectroscopic ellipsometry. In order to obtain the best approximation to the intrinsic dielectric response epsilon(E), the artifacts from surface overlayer in the measured have been minimized by the premeasurement surface treatments as well as the postmeasurement modeling procedure. The measured spectrum exhibited the critical-point structures for four interband transitions and their accurate energy values were obtained by applying the critical-point parabolic band model to the numerically calculated second-energy derivatives of the experimental data. The critical points at 3.27, 3.92, and 4.90 eV were identified as the E-1, A(1), and A(2) interband transitions from early optical reflectance studies. We also report a new critical-point structure at 3.63 eV. (C) 2008 American Vacuum Society.