  We present a measurement of the top quark mass using a sample of t-tbar
decays into an electron or a muon, a neutrino, and four jets. The data were
collected in p-pbar collisions at sqrt(s)=1.8 TeV with the Collider Detector at
Fermilab and correspond to an integrated luminosity of 109 pb^-1. We measure
the top quark mass to be 175.9 +/- 4.8(stat.) +/- 4.9(syst.) GeV/c^2.
