An increasing demand for multimedia data delivery coupled with reliance in best-effort networks, such as the Internet, has spurred interest on effective quality of service (QoS) management for multimedia streams. Since today’s multimedia applications are expected to run in physically heterogeneous environments composed of both wired and wireless components, we assess the efficiency of transport-layer solutions for multimedia traffic in heterogeneous networks. In order to quantify the performance on media delivery, we investigate the multimedia application requirements vs. the QoS provided by the underlying network. The chapter also provides means for the perceptual QoS assessment of voice and video streams. In the sequel, we describe some representative end-to-end congestion control schemes, identifying the mechanisms that are most suitable for multimedia traffic. Our analysis is complemented with conclusive performance studies which quantify video delivery, within the context of transport protocol support and efficiency.