The reaction power densities for the important nuclear fusion reactions are compared with the radiation losses due to Bremsstrahlung and cyclotron radiation. Some properties of an ionized plasma and the particle motions in such a plasma are discussed and methods of containing a plasma within magnetic confining fields are described. The present ideas on the stability of such confining fields, resulting from several theoretical studies, are outlined, and various means of heating the plasma are discussed. The main features of the experimental devices disclosed at Geneva in 1958 are compared, and the leading experimental results reported at the 1959 I.E.E. Convention on Thermonuclear Processes are reviewed.