A review is presented of the status of problems involving the interaction of matter and optical-band electromagnetic radiation of intensity such that any medium becomes a fully ionized plasma. The following are considered within the framework of the single-electron approximation in the case of nonrelativistic energies: stimulated bremsstrahlung and absorption of an electron in the field of a strong electromagnetic wave, stimulated two-photon Compton scattering, and scattering of electrons in the field of an intense standing electromagnetic wave (the Kapitza--Dirac effect). The role played by these processes in the heating of plasma by laser radiation is analyzed, as is the question of the possibility of obtaining amplification (negative absorption) of light in transitions in a continuous spectrum. The bibliography is brought up to date to the middle of 1971.