Dense, single-phased K-β -alumina polycrystals have been prepared from Al-oxyhydroxides by a direct sintering route. The samples were hot-pressed at temperatures between 1300-1500°C. All samples showed a very homogeneous microstructure without exaggerated grain growth. The sample sintered at 1300°C had a single phased β -alumina structure, whereas the 1500°C sample consists of a β/β -alumina mixture. The activation energies of all samples were about 0.4 eV, the ionic conductivities at 300°C, obtained by ac-impedance measurements, layed between 10 - 3 -10 - 4 S/cm. The similarity of the activation energies imply, that the conductivity of all samples is mainly restricted by grain boundary resistivities.