This study offers a theory of agreement within the framework of lexical-functional grammar. In this theory, verbal affixes may mark either grammatical or anaphoric agreement. In grammatical agreement, a NP bears an argument relation to the verb, while the verbal affix expresses redundantly the person, number, and gender class of the NP. In anaphoric agreement, the verbal affix is an incorporated pronominal argument of the verb, and the coreferential NP has a non-argument function—either as an adjunct of the pronominal argument, or as a topic or focus of the clause or discourse structure. Grammatical topics have syntactic properties deriving from a theory of discourse functions. The minimal difference between an incorporated pronoun and a grammatical agreement marker is the presence or absence of a semantic attribute in the lexical content of the affix. Likewise, the minimal difference between a subject NP and a topic NP is the function, rather than the phrase structure attributes of dominance, precedence, and category. This theory offers an explanation for the close relation between grammatical and anaphoric agreement, as well as clear criteria for distinguishing anaphoric and grammatical agreement by their discourse, syntactic, and even phonological effects. The Chicheŵa language (Bantu) has both grammatical agreement with the subject and anaphoric agreement with the object, and related languages show various distributions of these two agreement types.