The processing of subject-verb number agreement in sentence production by speakers of the standard dialect of the Brazilian Portuguese is investigated. The dissertation focuses on attraction errors and its main aim is to identify the factors that interfere in agreement processing and to provide a psycholinguistic account, which is compatible with assumptions of the Minimalist Program of Generative Linguistics. This work examines, in particular: i) the conditions that favor attraction errors and the syntactic properties which make an intervenient head to be considered as the agreement controller; ii) the role of morphophonological information on number provided by the DP subject modifiers; iii) the interference of conceptual number in agreement. Additionally, the work intends to distinguish, in structural terms, the DPs responsible for attraction errors from those DPs that allow a singular and a plural form of the verb - the so-called partitive constructions. A psycholinguistic procedure of grammaticality judgment is conducted in order to verify agreement processing differences between partitive constructions and complex DPS. The relevance of these topics is due to the fact that they enable a more comprehensive discussion on the autonomy of the syntactic formulator in language production. An extensive review of the existing literature was carried out and results are reported, concerning the interference from syntactic, semantic and morphophonological factors on agreement processing in different languages. Explanations provided by interactive and non-interactive models are discussed in this work. The minimalist conception of language is presented according to which agreement is described as a feature valuation process and a serial non-interactive production model is characterized, which incorporates a monitoring-parser that works in parallel with speech formulation - PMP model (parser monitored production). A total of 5 experiments with Portuguese speakers are reported. The results show an effect of markedness and linear distance between the subject and the verb, with more errors caused by non-marked (singular) subject heads that are linearly distant from the verb, and an effect of the structural position of the intervenient head, with a large number of errors for intervenient heads that are near to the upper phrasal marker of the DP and for heads which are inserted in PP arguments. A semantic effect of distributivity associated with an effect of markedness was also obtained. As far as morphphonological factors, number information of the determiner (and not of the noun) has shown to be critical to subject number identification. A revised and improved version of the PMP model is proposed that unifies possible explanations for agreement in terms of on an accessibility scale of the DP subject representation in the working memory and that takes into account parser predictions as a possible factor of interference in attraction errors. This interference would occur after the parsing of the DP and would affect the morphophonological encoding of the verb. In sum, the main argument of the thesis is that agreement errors do not occur in the syntactic computation and that the syntactic formulator works autonomously.