Weak interactions and symmetries

A few problems and recent results in weak interaction physics which have some implication in nuclear physics will be reviewed. After a brief discussion on parity non conservation in nuclei, the present experimental situation and the future plans for investigating lepton and baryon non conservation will be considered. I will discuss in particular experiments on double beta decay both to ground and to excited levels, also in view of a possible non-zero neutrino mass. The paper will be concluded by a review of the present and planned experiments on nucleon decay and on neutron-antineutron oscillations. (orig.)