  We examine the light quark masses in a standard--like superstring model in
the four dimensional free fermionic formulation. We find that the supersymmetry
constraints in the observable and hidden sectors eliminate all large
contributions to $m_u$ and $m_d$ and force them to be much smaller than the
other quark masses. The requirement for an acceptable Higgs doublet spectrum
results in $m_u<<m_d$. In these models a realistic $m_d$ can always be obtained
whereas $m_u$ is at most $10^{-5}~MeV$. For particular choices of flat
directions or vacua $m_u$ can be as small as $10^{-7}~MeV$ but cannot vanish.
