Two of the most exciting topics of current research in stochastic networks are the complementary subjects of stability and rare events. Both are classical topics that have experienced renewed interest motivated by new applications to emerging technologies. For example, new stability issues arise in the scheduling of multiple classes in semiconductor manufacturing, the so-called re-entrant lines, and a prominent need for studying rare events is associated with the design of telecommunication systems using the new ATM (asynchronous transfer mode) technology so as to guarantee quality of service. The objective of this volume is to present a sample of recent research problems, methodologies, and results in these two exciting and burgeoning areas. This volume originated from a workshop held at Columbia University in 1995 organized by Columbia’s Center for Applied Probability.