  We propose to probe the electroweak symmetry breaking sector by measuring the
effective couplings of the top quark to gauge bosons. Using precision LEP data,
we constrain the non--universal couplings of t-t-Z and t-b-W, parameterized by
$\kappa_{L}^{NC}$, $\kappa_{R}^{NC}$, $\kappa_{L}^{CC}$ and $\kappa_{R}^{CC}$,
in the electroweak chiral lagrangian framework. Different scenarios of
electroweak symmetry breaking will imply different correlations among these
parameters. We found that at the order of ${m_t}^{2}\log {\Lambda}^2$, in which
$\Lambda \sim 4 \pi v$ is the cut--off scale of the effective theory,
$\kappa_{L}^{NC}$ is already constrained by LEP data. In models with an
approximate custodial symmetry, a positive $\kappa_{L}^{CC}$ is preferred.
$\kappa_{L}^{CC}$ can be constrained by studying the direct detection of the
top quark at the Tevatron and the LHC. At the NLC, $\kappa_{L}^{NC}$ and
$\kappa_{R}^{NC}$ can be better measured.
