A computational account of VP ellipsis is described, in which VP's are represented in the discourse model as contextually dependent semantic objects. It is argued that this approach can handle examples that are not allowed by alternative accounts. An implementation is defined in terms of extensions to the Incremental Interpretation System. The treatment of VP ellipsis is analogous to that of pronominal anaphora. It is suggested that the recency and salience constraints commonly thought to apply to pronominal anaphora might apply in a similar way to VP ellipsis.