  Using data collected with the CLEO-III detector at the CESR e+e- collider, we
report on a first observation of the decay of the Upsilon(3S) to tau tau, and
precisely measure the ratio of branching fractions of Upsilon(nS),n=1,2,3 to
tau tau and mu mu final states, finding agreement with expectations from lepton
universality. We derive absolute branching fractions for these decays, and also
set a limit on the influence of a low mass CP-odd Higgs boson in the decay of
the Upsilon(1S).
