The energy band structures, density of states (DOS) and the optical properties of paraelectric cubic crystal KTaO3 have been calculated by the first principle pseudopotential using density functional theory in its local density approximation. The calculated band structure shows a direct band gap of 2.987 eV at the Gamma point in the Brillouin zone. The real and imaginary parts of the dielectric function and hence the optical constants such as i;,ff (the optical dielectric constant) and N-eff (the effective number of electrons) per unit cell are calculated. The calculated spectra are compared with the experimental results for KTaO3 and are found to be in good agreement with the experimental results. (c) 2007 Elsevier B.V. All rights reserved.