This document contains a formal syntax for the PL/CS programming language. As is customary, the defining context-free grammar generates a somewhat larger language than PL/CS. That is, only those restrictions conveniently expressed by context-free productions are incorporated in the definition. However, all legal PL/CS programs are contained in the language defined. With some exceptions, the formal syntax defines the language described in: Conway, R., "PL/CS - A Highly-Disciplined Subset of PL/C", Dept. of Computer Science, Cornell University, TR 76-273. The present report supersedes this earlier report as the document defining the syntax of the PL/CS subset.