Experiments on ?-decay.- A. General measurements.- 1. Identity of ?-particles and electrons.- 2. Maximum energies and half-lives.- 3. Maximum energies and half-lives. Experimental procedure.- B. Neutrino hunting.- 4. Neutrino emission from reactions other than nuclear ?-decay.- 5. Calorimetric mean energy measurements.- 6. Neutrino recoil experiments.- 7. Experiments on direct detection of neutrinos.- 8. Neutrino rest mass.- C. Spectral shapes and ft values.- 9. General discussion of shape measurements.- 10. Allowed transitions.- 11. Forbidden transitions.- 12. Deviations from the Fermi shape.- D. Polarization experiments.- 13. Introductory remarks.- 14. Electron polarization.- 15. The ?-decay of polarized nuclei.- 16. ?-?-polarization directional correlations.- 17. The neutron decay.- 18. The neutrino helicity.- E. Coupling constant determination.- 19. Introduction.- 20. Polarization of ?-particles.- 21. The neutron decay.- 22. Supporting evidence.- 23. Concluding remarks.- F. Electron capture.- 24. K capture.- 25. L/K capture ratios.- 26. Energy determination in electron capture.- G. Related reactions.- 27. Double ?-decay.- 28. Internal bremsstrahlung.- Concluding remarks.- General references.- Sachverzeichnis (Deutsch-Englisch).- Subject Index (English-German).