This study examined (a) the relationship between gesture and speech produced by children with specific language impairment (SLI) and typically developing (TD) children, and their mothers, during shared book-reading, and (b) the potential effectiveness of gestures accompanying maternal speech on the conversational responsiveness of children. Fifteen preschoolers with expressive SLI were compared with fifteen age-matched and fifteen language-matched TD children. Child and maternal utterances were coded for modality, gesture type, gesture-speech informational relationship, and communicative function. Relative to TD peers, children with SLI used more bimodal utterances and gestures adding unique information to co-occurring speech. Some differences were mirrored in maternal communication. Sequential analysis revealed that only in the SLI group maternal reading accompanied by gestures was significantly followed by child's initiatives, and when maternal non-informative repairs were accompanied by gestures, they were more likely to elicit adequate answers from children. These findings support the "gesture advantage" hypothesis in children with SLI, and have implications for educational and clinical practice.