Finite neutrino masses and mixings will lead to several effects which have been searched for in various experiments. First, the kinematic in weak decays of nuclei and mesons will be modified. Also the decay of heavy neutrinos into lighter ones becomes possible. Second, oscillations of neutrinos of one type into neutrinos of another type will occur which may be observable even if the masses are very small. Experiments using terrestrial and non-terrestrial neutrino sources have been performed. Third, provided neutrinos have Majorana masses, lepton-number-violating processes like neutrinoless double beta decay will take place. It is attempted here to review recent results from all these experiments, and to discuss the constraints they impose on neutrino masses and mixings.