New data for the total cross section
σ(e^+e^- → hadrons) in the charm and bottom
threshold region are combined with an improved theoretical analysis,
which includes recent four-loop calculations, to determine the
short distance \overline{MS} charm and bottom quark masses.
The final result for the \overline{MS}-masses,
m_c(3 GeV)=0.986(13) GeV and m_b(10 GeV)=3.609(25) GeV is
consistent with but significantly more precise than a similar
previous study.