  The study of the properties of the top quark is one of the main goals of the
Large Hadron Collider (LHC) physics program. The experimental precision
expected at the LHC requires the calculation of several top-quark related
observables beyond leading order in the strong coupling constant. In this work
we briefly review the status of the theoretical predictions for the top-quark
production processes at hadron colliders. Special attention is devoted to
recent progress in the calculation of next-to-next-to-leading-order corrections
to the top-quark pair production cross section.
