  The OZI rule have been tested in a number of experiments in a wide interval
of energies. It was found that the rule is fulfilled well, within few percent
of accuracy. The results of experiments with stopped antiprotons at LEAR
(CERN), where unexpected large violation (by a factor 3-70) of the OZI rule was
found, were quite surprising. Later experiments found strong violation of the
OZI rule not only in antiproton annihilation but also in reactions with protons
and pions.
  In the review we consider the phenomenology of the OZI rule, to what extent
it is valid in the hadron interactions. The experimental evidences of the large
OZI violation are discussed. The polarized strangeness model and its
explanation of the large OZI violation is discussed, the review of other
theoretical models is given.
