The Internet and the Grid are changing the face of high-performance computing. Rather than tightly-coupled SPMD-style components running in a single cluster, on a parallel machine, or even on the Internet programmed in MPI, applications are evolving into sets of collaborating components scattered across diverse computational elements. These collaborating components may run on different operating systems and hardware platforms and may be written by different organizations in different languages. Complete "applications" are constructed by assembling these components in a plug-and-play fashion. This new vision for high-performance computing demands features and characteristics which are not easily provided by traditional high-performance communications middleware. In response to these needs, we have developed ECho, a high-performance event-delivery middleware that meets the new demands of the Grid environment. ECho provides efficient binary transmission of event data with unique features that support data-type discovery and enterprise-scale application evolution. We present measurements detailing ECho's performance to show that ECho significantly outperforms other systems intended to provide this functionality, and that it provides throughput and latency comparable to the most efficient middleware infrastructures available.