  In this paper we consider mixed two-loop electroweak corrections to the top
quark propagator in the Standard Model. In particular, we compute the on-shell
renormalization constant for the mass and wave function, which constitute
building blocks for many physical processes. The results are expressed in terms
of master integrals. For the latter practical approximations are derived. In
the case of the mass renormalization constant we find agreement with the
results in the literature.
