This book is devoted to the investigation of the strongly interacting hadrons — to a quark model operating with effective color particles, constituent quarks, massive effective gluons and diquarks. The study of strong interactions based on effective constituent particles requires a solid ground of experimental data, which we now have at our disposal with the serious progress made in the investigation of hadrons, especially meson states. The present understanding of QCD applied to strong interactions can be distorted by prejudices. Therefore, the way followed by the quark model is to rely on the experiment and to restore the effective Hamiltonian on the basis of QCD on the one hand, and, on the other, of the spectral integral method.Baryon–baryon and antibaryon–baryon interactions are studied with the purpose of unambiguous applications of the written formulae to the interpretation of experimental data — to the observation of new meson and baryon resonances. The technique used is the spin-orbital momentum expansion of the amplitude. This method is our basic approach to the proper treatment of experimental data. The photon-induced reactions are also considered and the problem of form factors is discussed.Contents: Hadrons as Systems of Constituent Quarks; Systematics of Mesons and Baryons; Elements of the Scattering Theory; Baryon–Baryon and Baryon–Antibaryon Systems; Pion–Nucleon and Photon–Nucleon Collisions; Multiparticle Production Processes; Photon-Induced Hadron Production, Meson Form Factors and Quark Model; Spectral Integral Equation.