Network stability is an important issue that has attracted the attention of many researchers in recent years. Such interest comes from the need to ensure that, as the system runs for an arbitrarily length of time, no server will suffer an unbounded queue buildup. Over the last few years, much research has been carried out to gain an understanding of the factors that affect the stability of packet-switched networks. In this paper, we attempt to review the most noteworthy results in this area. We will focus on networks where the scheduling policy is of the FIFO type, which is, by far, the most widely adopted policy. We gather these results and present them in an organized manner. Furthermore, we also identify some directions open to future research. Ó 2007 Elsevier B.V. All rights reserved.