  We compare the physical reach of a Neutrino Factory in the 2+2 and 3+1
four-family models, with similar results in the two schemes; in both cases huge
CP-violating effects can be observed with a near detector in the $\nu_\mu \to
\nu_\tau$ channel. We also study the capability of long baseline experiments
(optimized for the study of the three-family mixing parameter space) in
distinguishing a three (active) neutrino model from a four-family scenario.
