  Neutral-current and charged-current deep-inelastic scattering at very high
four-momentum transfer squared (Q^2) have been studied in positron-proton
collisions at center-of-mass energy 300 GeV using the ZEUS detector at HERA. An
integrated luminosity of 47.7 $pb^{-1}$ was collected in the years 1994-1997.
Differential cross sections are presented for $Q^2 > 400 GeV^2$ and compared to
Standard Model predictions.
