An ad hoc wireless network (AWN) is a collection of mobile hosts forming a temporary network on the fly, without using any fixed infrastructure. Characteristics of AWNs such as lack of central coordination, mobility of hosts, dynamically varying network topology, and limited availability of resources make QoS provisioning very challenging in such networks. In this paper, we describe the issues and challenges in providing QoS for AWNs and review some of the QoS solutions proposed. We first provide a layer-wise classification of the existing QoS solutions, and then discuss each of these solutions. © 2004 Elsevier B.V. All rights reserved.