The intriguing problem of the identification of the source of the cosmic radiation has presented a challenge since its discovery some 60 years ago. Measurement of the energy and isotropy of the radiation showed conclusively that one obvious source, the Sun, was not the main source. Even in 1938 it was clear from the discovery of extensive air showers that the cosmic-ray spectrum extended to at least 1016 eV and continuously running monitors indicated that the departure from isotropy was no greater than the statistical uncertainty of the measurements (i.e. about 1%). Recent results have raised the maximum observed primary particle energy to higher than 1020 eV and the departure from isotropy for particulate radiation, to less than 0.01 % at 5 x 1011 eV and 1% at 1017 eV. To these striking facts must now be added the great wealth of detailed knowledge which has come from the immense advances in technology in the past 30 years. On the cosmic-ray side these advances range from the flying of detectors and sophisticated equipment on great balloons near the top of the atmosphere to the imaginative flights of spacecraft far out into the Solar System, well away from the confusing effects of the Earth’s atmosphere and the magnetosphere. Such experiments have given the relative abundances and the energy spectra of a variety of atomic nuclei and of electrons and positrons, and the intensity, energy and spatial distribution of X-rays and y-rays.