WHAT CAN WE LEARN FROM 3-PION INTERFEROMETRY

We address the question, what additional information on the source sha pe and dynamics can be extracted from three-particle Bose-Einstein cor relations. For chaotic sources the true three-particle correlation ter m is shown to be sensitive to the momentum dependence of the saddle po int of the source and to its asymmetries around that point. For partia lly coherent sources the three-pion correlator allows one to measure t he degree of coherence without contamination from resonance decays. We derive the most general Gaussian parametrization of the two- and thre e-particle correlator for this case and discuss the space-time interpr etation of the corresponding parameters.