  Extended technicolor (ETC) theories typically require ETC gauge bosons
lighter than of order 1 TeV, to perturbatively generate the $t$ quark mass. We
point out that explicit models of $t-b$ mass splitting also typically contain
additional TeV scale ETC gauge bosons transforming in the {\it adjoint} of
technicolor, leading to large weak-isospin-breaking effects observable in the
$\rho$ parameter. Viable ETC models may thus require a lowest ETC scale of
order 10 TeV, with relatively strong and finely tuned couplings to generate
$m_t$. Such models do not generate observable corrections to the $Zb{\bar b}$
vertex.
