We report two parallel experiments conducted in French and in English in which we induced subject–verb agreement errors to explore the role of syntactic structure during sentence production. Previous studies have shown that attraction errors (i.e., a tendency of the verb to agree with an immediately preceding noun instead of with the subject of the sentence) occur when a preverbal local noun disagrees in number with the subject head noun. The attraction effect was accounted for either by the proximity of the local noun to the verb in the linearised sentence (linear distance hypothesis)or by the processing simultaneity of the head and local nouns situated in the same clause (clause packaging hypothesis). In the current experiments, speakers were asked to complete complex sentential preambles. Contrary to the predictions of these two hypotheses, we found that agreement errors were more frequent following an intermediate modiŽer (e.g., *The threat-S to the presidents-P of the company-S ARE serious) than an immediately preverbal modifier (e.g., *The threat-S to the president-S of the companies-P ARE serious). It is suggested that attraction is determined by the syntactic distance between the interfering noun and the head noun at a stage of the grammatical encoding of the sentence during which syntactic units are organised into a hierarchical structure.