We measure the mass of the tau to be 1775.1 +/- 1.6(m(cn)(stat.)) +/- 1.0(m
(cn)(sys.)) MeV using tau from Z(0) decays. To test CPT invariance we compa
re the masses of the positively and negatively charged tau. The relative ma
ss difference is found to be smaller than 3.0 x 10(-3) at the 90%. confiden
ce level. (C) 2000 Elsevier Science B.V. All rights reserved.