The origin of negative values of the Wigner distribution function

The classical limit of the quantum Wigner distribution function is found to be either the classically defined Wigner distribution function or a perfec tly localized phase space distribution of interacting classical particles/o ptical rays. In the first case the negative values of the Wigner distributi on function are shown to be due to the nonlocal character of the wave field and are not a signature of the non-classical quantum states. The second ca se shows that the hidden assumption of interacting particles/rays, not expl icit in the quantum formulation, is a consequence of the nonlocal character of the quantum wavefunction.