CP invariance problem in the quantum chromodynamics

The CP-invariance problem in QCD is reviewed. Non-Abelian gauge fields are the basis for constructing modern models of both electroweak and strong interactions. A quasiclassical analysis of non-Abelian theories points out to the possibility of occurrence in these theories of the ground state degeneration related with the so-called topological charge. The presence of degeneration gives evidence of a complicated structure of the vacuum state in gauge theories, that structure leading to serious physical consequencies. In particular, the so-called theta-structure of the vacuum in QCD discussed of late years may lead to the P- and CP-invariance violation in strong interactions