  We report on a search for flavor-changing neutral-currents (FCNC) in the
production of heavy quarks in deep inelastic $\nu_{\mu}N$ and $\bar{\nu}%
_{\mu}N$ scattering by the NuTeV experiment at the Fermilab Tevatron. This
measurement, made possible by the high-purity NuTeV sign-selected beams, probes
for FCNC in heavy flavors at the quark level and is uniquely sensitive to
neutrino couplings of potential FCNC mediators. All searches are consistent
with zero, and limits on the effective mixing strengths $% | V_{uc}| ^{2}$, $|
V_{db}| ^{2}$, and $| V_{sb}| ^{2}$ are obtained.
