We present a measurement of the top quark mass using a sample of <t(t)
over bar> decays into an electron or a muon, a neutrino, and four jets
. The data were collected in <p(p)over bar> collisions at root s = 1.8
TeV with the Collider Detector at Fermilab and correspond to an integ
rated luminosity of 109 gb(-1). We measure the top quark mass to be 17
5.9 +/- 4.8(stat) +/- 4.9(syst) GeV/c(2).