Sr and Ba beta-alumina single crystals were prepared by a floating zone (FZ) method. Their electrical conductivities in air were measured by ac impedance spectroscopy in the temperature range between 873 and 1573 K. Both single crystals cleaved along the (0004) plane. The electrical conductivity in parallel to the cleavage plane was 10-100 times greater than that of perpendicular to the cleavage plane. Sr beta-alumina single crystal had higher electrical conductivity than Ba beta-alumina single crystal. (C) 2003 Elsevier Science B.V. All rights reserved.