  We show how to constrain the physical spectrum of walking technicolor models
via precision measurements and modified Weinberg sum rules. We also study
models possessing a custodial symmetry for the S parameter at the effective
Lagrangian level - custodial technicolor - and argue that these models cannot
emerge from walking type dynamics. We suggest that it is possible to have a
very light spin-one axial vector boson. However, in the walking dynamics the
associated vector boson is heavy while it is degenerate with the axial in
custodial technicolor.
