This paper presents an overview of international research on acquisition of French in the context of SLI, highlighting contributions this research has made to our current understanding of this pathology, but also to our understanding of the structure of French and, more generally, our understanding of the way the mind is organized for language. After a review of the fundamental characteristics of SLI (definition, prevalence, etiology, long-term prognosis, subtypes), with specific reference to the clinical setting in France, the paper provides an outline of the grammatical characterization of SLI in French, which is followed by a discussion of the notion of clinical marker for SLI. Proposals made to explain these findings in the context of cross-linguistic research on SLI are reviewed. The hypothesis that SLI is linked to how the language faculty proper interacts with performance systems is given particular attention, and support for this view is presented from work on SLI in French from study of specific constructions in children with SLI, from study of how older children with SLI and adolescents avoid certain constructions, and from studies in which subjects with SLI are compared with subjects learning French in other atypical contexts (deafness, epilepsy) or as a second language.