We present the result of a search for charged Higgs boson decays of the top quark, produced in pp̄ collisions at √s=1.8 TeV. When the charged Higgs boson is heavy and decays to a τ lepton, which subsequently decays hadronically, the resulting events have a unique signature: large missing transverse energy and the low-charged-multiplicity τ. Data collected in 1992 and 1993 at the Collider Detector at Fermilab, corresponding to 18.7±0.7 pb-1, exclude new regions of combined top quark and charged Higgs boson mass, in extensions to the standard model with two Higgs doublets.
