In this thesis the nature of argument structure in the Navajo sentence is identified, with particular focus on the complex system of incorporated pronouns, and anaphora and obviation in the language. It is argued that Navajo is a pronominal argument language, where arguments are incorporated pronouns, while nominals are adjuncts. Descriptions of syntactic devices for marking co- and disjoint reference of arguments, within the simple clause, across the clauses in complex sentences, and in discourse contexts are given. These devices include: the yi/bi- alternation, which I identify as a voice contrast confined to sentences with all third person arguments; the "fourth" person, used for obviation and for deference, and the parallel processing convention.