A scanning probe microscope was used to induce local, nonvolatile field effects in epitaxial, ferroelectric Pb(Zr_0.52Ti_0.48)O₃/SrRuO₃heterostructures. Field-effected regions with linewidths as small as 3500 angstroms were written by locally switching the polarization field of the Pb(Zr_0.52Ti_0.48)O₃layer; the electronic density of the underlying metallic SrRuO₃ layer was modified and the sheet resistance was changed by up to 300 ohms per square. This procedure is completely reversible and allows submicrometer electronic features to be written directly in two dimensions, with no external electrical contacts or lithographic steps required.