Heavy quark masses from sum rules in four-loop approximation

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 MS¯ charm and bottom quark masses. A detailed discussion of the theoretical and experimental uncertainties is presented. The final result for the MS¯-masses, mc(3GeV)=0.986(13)GeV and mb(10GeV)=3.609(25)GeV, can be translated into mc(mc)=1.286(13)GeV and mb(mb)=4.164(25)GeV. This analysis is consistent with but significantly more precise than a similar previous study.