  Neutrinos are likely the most poorly understood basic constituents of the
Standard Model. In order to investigate precisely their interactions one should
be able to create high intensity and well-collimated neutrino beams with known
flavor compositions. This is a challenging problem for neutrino experiments. We
propose a method of studying neutrino interactions based on the fact that a
charged lepton is able to manifest itself effectively, with a certain
probability, as a neutrino. The effective neutrino method may provide an
additional tool for probing neutrino-induced reactions at $e^+e^-$ and $ep$
colliders as well as at other facilities that use charged lepton beams. We
derive the distributions of the effective neutrinos in the charged leptons and
give examples of application of the method to electron-positron collisions.
