  We present estimates of the masses of light quarks using lattice data. Our
main results are based on a global analysis of all the published data for
Wilson, Sheikholeslami-Wohlert (clover), and staggered fermions, both in the
quenched approximation and with $n_f=2$ dynamical flavors. We find that the
values of masses with the various formulations agree after extrapolation to the
continuum limit for the $n_f=0$ theory. Our best estimates, in the MSbar scheme
at $\mu=2 GeV$, are $\mbar=3.4 +- 0.4 +- 0.3 MeV$ and $m_s = 100 +- 21 +- 10
MeV$ in the quenched approximation. The $n_f=2$ results, $\mbar = 2.7 +- 0.3 +-
0.3 MeV$ and $m_s = 68 +- 12 +- 7 MeV$, are preliminary. (A linear
extrapolation in $n_f$ would further reduce these estimates for the physical
case of three dynamical flavors.) These estimates are smaller than
phenomenological estimates based on sum rules, but maintain the ratios
predicted by chiral perturbation theory. The new results have a significant
impact on the extraction of $\epsilon'/\epsilon$ from the Standard Model. Using
the same lattice data we estimate the quark condensate using the
Gell-Mann-Oakes-Renner relation. Again the three formulations give consistent
results after extrapolation to $a=0$, and the value turns out to be
correspondingly larger, roughly preserving $m_s \vev{\bar \psi \psi}$.
