  The physics impact of a precise determination of the top-quark mass, m_t, at
the Linear Collider (LC) is discussed, and the results are compared with the
prospective accuracy at the LHC. The importance of a precise knowledge of m_t
for electroweak precision observables and for Higgs physics in the MSSM is
pointed out in particular. We find that going from hadron collider to LC
accuracy in m_t leads to an improvement of the investigated quantities by up to
an order of magnitude.
