All papers have been peer reviewed. This was the 4th conference arranged by ICMM on probabilistic foundations of classical and quantum physics. The first three conferences took place in 2000, 2002, and 2004. Some closely related conferences are Bohmian Mechanics 2000 and Quantum Theory: Reconsideration of Foundations 2001, 2003, and 2005. The main aim of these conferences is to understand the role that probability plays in the foundations of physics, theoretical as well as experimental, classical as well as quantum. In this conference, as well as during our previous conferences, we are glad to welcome a fruitful assembly of theoretical physicists, experimenters, mathematicians, and even philosophers interested in the foundations of probability and physics. Among important topics discussed during the conference were the probabilistic foundations of quantum mechanics, as well as the foundations of probability itself, the formation theory, quantum computing, quantum cryptography, quantum teleportation, quantum fluctuations in relation with stochastic electrodynamics, Bohmian mechanics, measurement theory, completeness and incompleteness of quantum mechanics, macroscopic quantum systems, experiments on quantum nonlocality and locality, Bell's inequality, entanglement; philosophical problems raised by quantum mechanics, and mathematical formalism. A special session devoted to the Bayesain approach to classical and quantum probability was organized.
