  Leading QCD vacuum polarization contributions to the electroweak parameter
$\delta\rho$ are evaluated numerically using several different prescriptions
for the gluon self-energy. Simple theoretical estimates of the asymptotic
behavior are given. The results show a significant contribution from the
leading infrared renormalons when $\delta\rho$ is expressed in terms of the
top-quark pole mass and its absence when the $\msbar$ running mass is employed.
The calculations are applied to estimate higher order QCD contributions to
$\delta\rho$.
