A major objection to top-down accounts of lexical recognition has been that they are incompatible with an account of acquisition, it being argued that bottom-upsegmentation must precede lexical acquisition. We counter this objection by presenting a top-down account of lexical acquisition. This is made possible by theadoption of a flexible criterion as to what may constitute a lexical item during acquisition, this being justified by the extensive evidence of children’s undersegmentation. Advantages of the top-down account offered over the bottom-up alternatives are that it presents a unified account of the acquisition of a lexicon and segmentation abilities, and is wholly driven by the requirements of comprehension. The approach described has been incorporated into an integrated model of acquisition processes, the incremental learning of which captures the gradual nature of child language development.