Research on sluicing has not yet reached consensus on whether the identity condition on this ellipsis construction is syntactic or semantic. Evidence from Chamorro and English is presented that over and above semantic identity, sluicing requires limited syntactic identity. The limited syntactic identity condition involves argument structure on the one hand and abstract Case on the other. This approach is shown to account for a range of novel and familiar sluicing patterns in the two languages. It also provides new evidence for the idea that the Chamorro antipassive is an implicit argument construction.