This is a lecture given at the Gif Summer School held in 1992 in Montpellier. It contains three chapters. These are devoted to neutrino oscillations, to the nuclear reactors used as neutrino sources, and to the experiments performed with neutrinos from nuclear reactors, respectively. The first chapter offers a theoretical frame, the second discusses the investigation capabilities of nuclear reactors as neutrino sources while the last one describes the experimental aspects. These aspects are related to the neutrino flux measurement and the flavor oscillation, the search for neutrino oscillation, the neutrino scattering on electrons, the neutrino decay, the coherent neutrino scattering on nuclei and the electron neutrino-electron antineutrino oscillations implied by the Majorana nature of neutrinos. In concluding the author points to the possible ways of refining these extremely subtle experiments, which will be approached in the near future. 117 refs., 9 figs., 11 tabs.