Extended technicolor contribution to theZbbvertex

We show that the flavor-diagonal gauge boson of the extended technicolor theory contributes with opposite sign to the standard model correction for the Zbb vertex. This mecahnism can naturally explain the deviation of the CERN LEP result from the standard model prediction for the partial width Γ(Z→bb¯). A smaller value of the QCD coupling, ${\mathrm{\alpha }}_{\mathit{s}}$(${\mathit{m}}_{\mathit{Z}}$)≃0.115, is then preferred by the Γ(Z→hadron) data, which is consistent with both the recent lattice QCD estimate and the Particle Data Group average.