  The motion of neutral particles with magnetic moments in an inhomogeneous
magnetic field is described in a semi-classical framework. The concept of
Coherent Internal States is used in the formulation of the semiclassical
approximation from the full quantum mechanical expression. The classical
trajectories are defined only for certain spin state, that satusfy the
conditions for being Coherent Internal State. The raalibility of Stern-Gerlach
experiments to measure spin projectons is assessed in this framework.
