We report the observation of a ferroelectric field effect in the conducting oxide SrRuO3using Pb(Zr0.52Ti0.48)O3/SrRuO3epitaxial heterostructures. Upon reversing the polarization of the ferroelectric Pb(Zr0.52Ti0.48)O3layer, we measured a 9&percent; change in the resistance of a nominally 30 Å SrRuO3film at room temperature. This change was nonvolatile for a period of several days. Conductivity measurements taken between 4.2 and 300 K are consistent withn-type conduction throughout this temperature range. Hall effect measurements also yieldn-type conduction, withn≈2×1022electrons/cm3, and furthermore allow us to understand quantitatively the magnitude of the observed resistivity change. ©1997 American Institute of Physics.