This conference follows those held at the ICTP in 1993, 1996 and 1999. It is thus part of an established tradition of excellence aimed at the interdisciplinary, critical confrontation of the methods by which the basic concept of "quantum interference" is investigated in the most recent experiments involving various kinds of particles: photons, neutrons, electrons, excitons, atoms. A great deal of attention will be devoted to the interference properties of extended, multiparticle systems e.g. in the contexts of quantum computation, "Schroedinger-cat" zoology and Bose-Einstein atom condensation. Accordingly, quantum nonlocality, entanglement, teleportation, decoherence, quantum entropy and thermodynamics will become the key words of a large part of the Conference.