Four-Neutrino Mixing and Long-Baseline Experiments

We consider the two four-neutrino schemes that are compatible with all neutrino oscillation data. We present the range of the corresponding mixing parameters allowed by the results of neutrino oscillation experiments. We discuss the implications for long-baseline experiments and we suggest the possibility to reveal the presence of CP-violating phases through a comparison of the oscillation probability measured in long-baseline experiments with the corresponding average oscillation probability measured in short-baseline experiments.