The paper examines word order variation in spoken Brazilian Portuguese. It is first demonstrated that arguments of transitive clauses have fixed word order. Attention is then paid to intransitive clauses, whose single arguments may alternate between pre-verbal and post-verbal position. Presentative/Existential clauses are shown to take categorically post-verbal arguments. This grammaticization appears to be highly functionally motivated, as these clauses introduce new information into the discourse. For other types of intransitive clauses, alternation between pre-verbal and post-verbal position could not only be related to information flow (new vs. given), but also to other discourse factors such as persistence, distance of previous mention, as well as to semantic factors (animacy vs. inanimacy, semantic frame).