The book summarizes the results of solar cosmic ray (SCR) investigations since 1942. The present monograph, unlike the reviews published earlier, treats the problem in self-contained form, in all its associations-from fundamental astrophysical aspects to geophysical, aeronautical and cosmonautical applications. It includes a large amount of new data, accumulated during the last several decades of space research. As a result of the "information burst" in space physics, there are a lot of new interesting theoretical concepts, models and ideas that deserve attention. The author gives an extensive bibliography, which covers non-partially the main achievements and failures in this field. The book will be helpful for a wide audience of space physicists and it will be relevant to graduate and postgraduate courses. The book will serve as a reference work for researchers and students in solar physics and astrophysical plasma physics, as well as in cosmic rays physics, astroparticle physics, space science, solar-terrestrial relations, geophysics and those researching space weather problems, especially the problems of radiation hazard in space.