  This work discusses critically the prospects of measuring CP and T violation
effects in high energy neutrino factories. For this purpose we develop, in the
standard framework with three neutrino flavors, simple expressions for the
oscillation probabilities in matter that are valid for high E_nu. All CP
violating effects vanish as E_nu^(-3) and are very difficult to detect with
high energy neutrinos. A significantly easier task is the determination of the
absolute value |delta| of the phase in the neutrino mixing matrix that controls
the CP and T violation effects, performing precision measurements of the CP and
T conserving part of the oscillation probabilities.
