Although grammatical agreement or concord is widespread in human languages, linguistic theorists have generally treated agreement phenomena as secondary or even marginal. All the papers in this volume, however, take agreement phenomena seriously, as presenting either a general issue in theory construction or a descriptive problem in particular types of languages. The theoretical perspectives range from purportedly theory-neutral typological frameworks to assumptions about the validity of one or another current formal model. Further, the degree of generality ranges from a universalist nature-of-human-language agenda to concern with one or another aspect of grammatical agreement or with agreement in a single language or language group.