Measurement of the tau -lepton mass

Using data from the CLEO II detector at CESR, we measure the [tau]-lepton mass by exploiting the unique kinematics of events in which both [tau]'s decay hadronically. The result is [ital m][sub [tau]]=1777.8[plus minus]0.7[plus minus]1.7 MeV/[ital c][sup 2]. By comparing our result with other measurements near [tau]-pair threshold, we extract an upper limit on the [tau]-neutrino mass of 75 MeV/[ital c][sup 2] at 95% confidence level.