  In technicolor theories a large radiative correction to the Zbb vertex
generally emerges, because of the large top quark mass and SU(2)_L gauge
symmetry. The correction can give us an explanation for the deviation of the
experimental value of R_b from the standard model prediction. However,
generally the T parameter becomes unacceptably large. We show that in the
one-family technicolor model recently proposed by the authors all the S, T, and
U parameters can be consistent with the experimental bounds while the observed
anomaly of R_b is naturally explained.
