  Limits on the Higgs boson mass restrict CKM mixing of a possible fourth
family beyond the constraints previously obtained from precision electroweak
data alone. Existing experimental and theoretical bounds on the Higgs mass
already significantly restrict the allowed parameter space. Zero CKM mixing is
excluded and mixing of order the Cabibbo angle is allowed. Upper and lower
limits on 3-4 CKM mixing are exhibited as a function of the Higgs mass. We use
the default inputs of the Electroweak Working Group and also explore the
sensitivity of both the three and four family fits to alternative inputs.
