An ad hoc network is a collection of computers (nodes) that cooperate to forward packets for each other over a multihop wireless network, Users of such networks may wish to use demanding applications such as videoconferencing, Voice over IP, and streaming media when they are connected through an ad hoc network. Because overprovisioning, a common technique in wired networks, is often impractical in wireless networks for reasons such as power, cost, and government regulation, Quality of Service (QoS) routing is even more important in wireless networks than in wired networks. Though a number of QoS-routing protocols have been proposed for use in ad hoc networks, security of such protocols has not been considered. In this paper, we develop SQoS, a secure form of QoS-Guided Route Discovery for on-demand ad hoc network routing. SQoS relies entirely on symmetric cryptography. Symmetric cryptographic primitives are three to four orders of magnitude faster (in computation time) than asymmetric cryptography. In addition, we show that in general, existing QoS-Guided Route Discovery can, for a single Route Discovery, transmit a number of packets exponential in the number of network nodes, creating an opportunity for Denial-of-Service (DoS) attacks. SQoS limits this overhead to be linear in the number of network nodes by providing the source with control over which Route Requests are forwarded.