  The value of the light quark masses combination $m_u + m_d$ is analized using
QCD-Hadron Duality. A detailed analysis of both the perturbative QCD [to
four-loops] and the hadronic parametrization needed is done. The result we get
is $[m_u + m_d] (1 GeV^2) = (12.8 \pm 2.5)$ MeV ($[m_u + m_d] (4 GeV^2) = (9.8
\pm 1.9)$ MeV) in the $\barMS$ scheme.

High Energy Physics - Phenomenology