The focus of this paper is on the relation between syntax and prosody, by discussing the role of the empty syntactic categories in the application of the stress shift rule. The discussion about the influence of empty categories on phonological processes is not new. Usually, phonology papers argue that the access to syntax is indirect, and there is no access to phonological empty syntactic categories (cf. NESPOR; VOGEL, 1986). However, Santos (2002) argues that phonological empty syntactic categories can intervene on the rhythmic organization of utterances. She defends that pro intervene on stress shift rule, while trace is not taken into account for that rule. In order to show that, she tests utterances with stress clash between verb and adverb.In this presentation, the syntactic structures with verbs which can have a transitive or intransitive reading are tested with pro. The hypothesis is that when there is a transitive reading, the stress clash can not be solved. In the sentences where the intransitive reading is possible, there is no pro between the verb and adverb, and the stress shift rule is allowed. This prediction can be used as an evidence which favors Galves (1989) analysis that null object in Brazilian Portuguese is a pro, and not a trace.