We present results of a direct search for charged Higgs production
from ppbar collisions at sqrt s = 1.8 TeV at Fermilab's Tevatron collider
using the CDF detector.  An expanded Higgs sector containing charged Higgs
bosons is a persistent feature of candidate theories to replace the Standard
Model.  The minimal supersymmetric extension of the Standard Model, for
example, predicts that the dominant decay mode of the top quark is t -> H^+ b
-> pi^+ nu b for large values of tan b.  We use the hadronic decays of the tau
lepton in this channel to exclude charged Higgs bosons with M_H^+/- < 140
GeV/c^2 for large tan B.