The linguistic literature abounds with discussions of phi-feature inflection. The formalist tradition has, in a variety of ways, approached this phenomenon predominantly in terms of an agreement relationship between two terms of a syntactic structure-for instance, the subject and the finite verb (typically showing agreement for person and number), or the object and a past participle (which, e.g. in the Romance languages, may agree for number and gender, but not for person). But not all these agreement relationships affect all phi-features equally, which raises the question of whether there is to be a unified approach to phi-features in general. And two terms that can entertain an agreement relationship for certain phi-features do not seem to engage in such agreement every time they might be expected to so do. On the surface, plural subjects can co-occur with singularly inflected finite verbs, and vice versa; and sometimes a subpart of the subject seems to control the selection of the inflection on the finite verb, in so-called 'attraction' cases. These kinds of phenomena give rise to an in-depth exploration of the nature and reality of agreement relationships, including the possibility of an analysis treating phi-featural properties as autonomous vis-à-vis one another, assigned to each term separately, not under agreement. This special issue brings together a collection of papers and commentaries reflecting on these matters in various ways. In this introduction, I set the stage for the discussion to follow.