Not all children learn language effortlessly. Between 3% and 5% of children have a significant limitation in language ability without any apparent explanation (hearing impairment, low verbal intelligence test scores, psychological problems or neurological damage) which could explain these difficulties (Stark & Tallal, 1981). This limitation in language learning, called Specific Language Impairment (SLI), is characterized by a large heterogeneity in verbal symptoms. However, relatively homogeneous subgroups of SLI children can be identified (Rapin & Allen, 1987) and several studies have focused on specific SLI subsamples: Familial SLI (Gopnik, 1990), Semantic-pragmatic SLI (Adams & Bishop, 1989) or Grammatical SLI (Van der Lely, 1993, 1994, 1997). The latter category encompasses children with disproportionate impairment in grammatical comprehension and expression of language. Although very few children qualify for the deficiencies proposed by Van der Lely to be considered as G-SLI (Bishop, Bright, James, Bishop & Van der Lely, 2000), deficits in the use and the understanding of morphosyntactic information remain a hallmark of specific language impairment.