Renormalon contributions to δrho

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 $\delta\rho$.