  I consider selected (most important according to my own choice) unsolved
problems in particle theory, both those related to extensions of the Standard
Model (neutrino oscillations, which probably do not fit the usual
three-generation scheme; indications in favour of new physics from
astrophysical observations; electroweak symmetry breaking and hierarchy of
parameters) and those which appear in the Standard Model (description of strong
interactions at low and intermediate energies).
