  The prospects of measuring the leptonic angles and CP-odd phases at a {\em
neutrino factory} are discussed in the scenario of three active plus one
sterile neutrino, motivated by the $\nu_\mu \raw \nu_e$ LSND signal.
Sensitivity to the MNS mixing matrix angles at $O (10^{-3})$ is achieved with a
1 T detector at $\sim 1$ km from the source, whereas leptonic CP-violation can
be measured through tau detection with a 1 kT detector at $\sim 100$ km.
