  The following lectures concern with the quark structure of hadrons made up
from light quarks. The symmetries of strong interaction were the only
instruments used for the description of this structure.
  The models of hadrons (there are a lot of them) were not considered. There
was not also considered the structure of hadrons with heavy quarks. The first
round of problems (models of hadrons) is not considered because of its
unexhaustability. The second round of problems (hadrons with heavy quarks) is
not considered because of the physics of heavy flavors tends mainly to
electroweak interaction and will be considered in the course of electroweak
interactions.
  Therefore, the presented here course, being the self-bounded part of the
theory of elementary particles, is considered separately.
  These lectures were formed from 1989 and are the part of the set of courses
on the theory of fundamental interactions for the students of Moscow Physical
Technical Institute. The basic source of the lectures was the unpublished
manuscript "Hadrons and quarks" by L.B. Okun. Another source was the "Lectures
on the theory of unitary symmetry in elementary particle physics" by Nguen Van
Hieu (Atomizdat, Moscow 1967). The list of references (due to its smallness) is
absent.
