This chapter introduces adaptivity and Internet applications. Its focus is on streaming media, i.e., in particular, the streaming of audio over the web. It argues that to achieve good quality end-to-end performance (between client and server), adaptive architectures provide a better solution in terms of scaleability and network fairness than that of reservation techniques. However, this is at the cost of reducing the 100% end-to-end performance guarantee. The Kendra adaptive content delivery architecture is discussed as a proof of concept highlighting the parameters that most affected performance. Kendra is then critiqued in terms of alternative solutions showing where future research in this area could lie.