This paper provides an account of be going to and will within the framework of Relevance Theory (Sperber & Wilson, 1986, 1995. Because of the range of interpretations derived from the use of these expressions in different contexts, many previous accounts have characterized them as polysemous. This polysemy has been attributed to semantic retention, whereby both old (lexical) and new (grammaticalized) meanings are recovered in certain contexts. The aim of this paper is to demonstrate: (i) that although be going to does exhibit semantic retention, in a relevance-theoretic framework this does not entail polysemy, and (ii) that interpretations of will previously attributed to semantic retention are, in fact, pragmatically derived, and hence will is also monosemous.