CHILL1 is the high-level programming language defined and recommended by the International Telegraph and Telephone Consultative Committee (CCITT) for the production of software for telecommunication systems. The purpose of this document is to provide an overview of the main features of CHILL, by concentrating on their semantics and use, rather than on their syntax and subtle exceptional cases. The reader is not required to be familiar with CHILL, but is supposed to know at least another high-level programming language, such as Pascal.