Transparent single crystals of La1-xSrxScCO3 (x=0-0.03) were grown by the floating zone method. The electronic structure near the fundamental absorption edges of these perovskite-type proton conductors was first investigated in the ultraviolet and visible region by optical absorption spectroscopy. The fundamental absorption edge was observed around 5.8 eV. The optical absorption edge around 4.5 eV may be considered to be due to the acceptor level in the band gap. IR absorption spectra suggested that protons occupy intra- or inter-SCO6 octahedral sites. The number of protons at the inter-SCO6 Octahedral sites was found to affect strongly the electrical conductivity. (C) 2006 Elsevier B.V. All rights reserved.