  We compute the strange and the average up/down quark masses in the quenched
approximation of lattice QCD, by using the O(a)-improved Wilson action and
operators and by implementing the non-perturbative renormalization. Our
computation is performed at four values of the lattice spacing, from which we
could extrapolate to the continuum limit. Our final result for the strange
quark mass (in the MSbar scheme) is ms(2 GeV) = (106 +/- 2 +/- 8) MeV. For the
average up/down quark mass we have ml(2 GeV) = (4.4 +/- 0.1 +/- 0.4) MeV. The
ratio ms/ml = (24.3 +/- 0.2 +/- 0.6).
