The 3GPP packet-switched streaming service (PSS) is a standard for audio and video streaming to handheld 2.5G and 3G terminals and provides a complete streaming and download framework for commercial content. This article gives an overview of the PSS standard and in particular the support for adaptive streaming in PSS. We first describe the concept of streaming media and motivate the development of the PSS standard. Next, an introduction and overview of the PSS standard is given, followed by a detailed walkthrough of the adaptive streaming features. Finally, we present an example of 3GPP PSS-compliant adaptive streaming performed in a real client/server implementation. The proposed scheme is shown to be able to substantially improve the streaming quality under 2.5G and 3G network channel scenarios.