In most theoretical and descriptive treatments of English proforms it seems to be accepted that proforms replace constituents in underlying structure (i.e. phrases or clauses). The aim of the present article is to challenge this assumption. It will be demonstrated that a great many fully acceptable uses of proforms turn out to be quite problematic for the view of proforms as corresponding either to constituents or to semantic and/or syntactic units in underlying representation; nor, it turns out, do proforms necessarily refer to or denote a single (identifiable, retrievable or inferrable) entity. After a brief summary of the relevant literature, the article presents a detailed examination of the actual function and use of English proforms, focusing on a number of frequently used proforms: (i) the indefinite pronoun one, (ii) the predicative proform do so, (iii) the demonstrative pronouns that and those and (iv) certain uses of the personal pronouns we/us and you. On the basis of attested examples, it is argued that these proforms do not necessarily express a unit at any level of underlying representation. Instead an alternative account of the use of proforms is suggested, using the theory of Functional Discourse Grammar, which, with its four different levels of analysis (representing pragmatic, semantic, morphosyntactic and phonological information), possesses the kind of flexibility needed to deal with English proforms in a consistent and unified manner. Finally, an attempt is made to explain some of the constraints on the flexible system proposed.