A detailed account of the English existential construction in the framework of functional grammar. A structural analysis of the construction leads to an embedded predication analysis; an analysis of definite NPs in existentials leads to the argument that the definiteness restriction is a misnomer; and a study of the predicate types allowed shows that the restrictions in this respect can be accounted for in terms of constraints on use. The central point is that by considering constraints on the form of existentials in the light of how they may be used it may be possible to gain insight into the formal properties of the English existential construction; and functional grammar appears to offer the right framework for this way of approaching the problem.