At the Naval Research Laboratory, we are build-ing a deterministic parser, based on principles pro- posed by Marcus, that can be used in interpreting military message narrative, A central goal of our project is to make the parser useful for real-time applications by constraining the parser’s actions and so enhancing its efficiency. In this paper, we propose that a parser can determine the correct structures for English without looking past the "left corner" of a constituent, i.e. the leftmost element of the constituent along with its lexical category (e.g. N, V, Adj). We show that this Left Corner Con-straint, which has been built into our parser, leads quite naturally to a description of verb comple-ments in English that is consistent with the tidings of recent linguistic theory, in particular, Chomsky' s government and binding (GB) framework.