Using data collected at the CDF detector at the Fermilab Tevatron
between 1992 and 1995, we measure the top quark branching fraction BF(t ->
Wb)/BF(t -> Wq) and from it extract the first direct measurement of the CKM
matrix element Vtb.  Additionally, we report on searches for the Flavor
Changing Neutral Current decays t -> c gamma and t -> c Z.  No evidence of
physics beyond the Standard Model is observed.