This thesis investigates the span of encoding in the production of French adjective-noun phrases (NPs). While speaking, speakers do not only articulate the portion of the sentence they have already encoded, they are also planning the rest of the sentence. The question then is what amount of planning scope is necessary to insure fluency in the production of a multiword utterance? This unit of encoding must be large enough to guaranty speech fluidity but small enough to prevent cognitive overload and speech outburst. Similarly, we investigate whether this amount of encoding varies and if it does, which constraints determine it. In a series of behavioural and ERP studies, we compare the production of one-word NPs to two-word NPs of two different syntactic structures (adjective+noun and noun+adjective). Our results show that the span of encoding is not constrained by syntactic structure and that the minimal unit of encoding varies across speakers.