  We compute the strange quark mass $m_s$ and the average of the $u$ and $d$
quark masses $\hat m$ using full lattice QCD with three dynamical quarks
combined with experimental values for the pion and kaon masses. The simulations
have degenerate $u$ and $d$ quarks with masses $m_u=m_d\equiv \hat m$ as low as
$m_s/8$, and two different values of the lattice spacing. The bare lattice
quark masses obtained are converted to the $\msbar$ scheme using perturbation
theory at $O(alpha_s)$. Our results are: $m_s^\msbar$(2 GeV) = 76(0)(3)(7)(0)
MeV, $\hat m^\msbar$(2 GeV) = 2.8(0)(1)(3)(0) MeV and $m_s/\hat m$ =
27.4(1)(4)(0)(1), where the errors are from statistics, simulation,
perturbation theory, and electromagnetic effects, respectively.
