  We examine the structure of the quaternion group $Q_8$ and its possible
application to the physics of flavor. We find that a $Q_8$ family symmetry is
suitable to explain the difference between quark and lepton mixing patterns.
Distinctive phenomenological predictions are derived for the neutrino sector
and the electroweak Higgs sector. We also show how the $Q_8$ symmetry
suppresses the effective operators which mediate proton decay.
