This document defines the Call Processing Language (CPL)@ a language to describe and control Internet telephony services. It is designed to be implementable on either network servers or user agents. It is meant to be simple@ extensible@ easily edited by graphical clients@ and independent of operating system or signalling protocol. It is suitable for running on a server where users may not be allowed to execute arbitrary programs@ as it has no variables@ loops@ or ability to run external programs.