  A short introduction summarizes the experimental high energy field of
neutrino oscillations and the oscillation notations. Then the results obtained
by experiments on atmospheric neutrino oscillations are summarized and
discussed. At the beginning of the new century a number of long baseline
neutrino beams became available. The results obtained by different long
baseline neutrino oscillation experiments are considered, including the first
possible event $\nu_{\mu} \rightarrow \nu_{\tau}$ in appearance mode. Finally
conclusions and perspectives are discussed.
