This study, the first in the series Studies in English Language, is concerned with the functional and communicative foundations of English grammar, and takes as its specific focus the study of infinitival complement clauses. Much of the illustrative material is taken from the Survey of English Usage at University College London. The work draws on a large amount of data from spontaneous speech, and provides a close analysis of numerous examples in their authentic discourse context. It is based on the assumption that syntactic structures are closely connected with, and partly determined by, conventions of human discourse and the speaker's or writer's desire to express meaning efficiently. The ample documentation will appeal to those interested in the structure of modern British English. For those interested in syntactic theory and discourse, this is an empirical contribution to the debate on discourse-based approaches to functional syntax.