The sintering behavior of alumina containing different amounts of calcium-aluminum-silicate glass as sintering aid was analyzed under AC electric fields between 0 and 150V/cm. Liquid phase sintering was enhanced by the electric field, and flash sintering behavior depending on the current density and power dissipation within the specimen could be observed. Current flowed only through the liquid phase at high temperature and enhanced the densification process by two effects: Joule heating and athermal response of the viscous liquid under the electric field. Joule heating increased the temperature within the specimen, whereas the applied electric field reduced the viscosity of the liquid phase promoting a more effective matter transport.