We present an overview of the theory of high--Q^2 deep inelastic scattering.
We focus in particular on the theoretical uncertainties in the predictions for
neutral and charged current cross sections obtained by extrapolating from lower
Q^2.Comment: 10 (Latex) pages, including 6 embedded figures, uses epsfig.sty,
ioplppt.sty and iopl12.sty; Plenary talk presented at the 3rd UK
Phenomenology Workshop on HERA Physics, Durham, September 1998, to be
published in the Proceeding