  Talk given at the Conference on Fundamental Interactions of Elementary
Particles, ITEP, Moscow, Oct. 1995. The paper reviews the current status of
knowledge concerning m_u, m_d and m_s. Qualitative aspects of the resulting
picture for the breaking of isospin and eightfold way symmetries are discussed.
At a more quantitative level, the review focuses on the chiral perturbation
theory results for the masses of the Goldstone bosons. The corresponding bounds
and estimates for the ratios m_u/m_d and m_s/m_d are described in some detail.
