Recent experimental results on the cross section for electron-positron annihilation into hadrons
in the low energy region between roughly 3 GeV and 10 GeV, combined with an improved
determination of the strong coupling and increasingly precise theory results on sum rules have
lead to determinations of charm- and bottom-quark masses with accuracies of around 10 MeV.
The final results, expressed in the MS scheme, have lead to $m_{c}$ (3 GeV) = 993(8) MeV and
$m_{b}$ $(m_{b})$ = 4163(16) MeV, and are thus among the most precise determinations of these standard
model parameters. These results are, furthermore, nicely consistent with completely independent
lattice results and allow precise predictions for a number of experimental observables like Higgs
decays into charm- or bottom-quarks. A critical analysis of the theoretical and experimental un-
certainties of this analysis is presented in the following.