The status of ''polarized fusion''

After an introduction into the essentials of nuclear fusion reactions, being considered for future energy production in fusion reactors, different aspects of using ''polarized'' particles as fuel are discussed. Special emphasis is given to the four-nucleon system and the D+D reactions. The status of the theory and the experimental data are presented. Predictions for observables in the framework of existing theoretical approaches are given. The necessity of carrying out direct spin-correlated cross-section measurements is accentuated. Details of a future experiment are proposed. (orig.)