Purpose: The authors investigated mental representations of Piagetian conservation tasks in children with specific language impairment (SLI) and typically developing peers. Children with SLI have normal nonverbal intelligence; however, they exhibit difficulties in Piagetian conservation tasks. The authors tested the hypothesis that conservation difficulties may be due to the degree to which children with SLI rely on external perceptual features of the task as opposed to internal cognitive knowledge about transformation. Method: Twenty-nine children participated, 12 children with SLI (ages 7;0-10;5) and 17 typically developing peers (ages 5;4-10;9) who were matched either on chronological age (CA) task or on judgments on the conservation task (conservation matched [CM]). Children solved conservation tasks and then explained their reasoning. Explanations produced in speech and gesture were analyzed. Results: In speech, children in the SLI group expressed proportionately fewer internal explanations than the CA group, but a similar proportion of internal explanations as compared with the younger CM group. In gesture, children with SLI did not differ from either CA or CM children. Conclusions: Children with SLI have weak internal representations of the concept of conservation, similar to those of younger children. Conservation representations appear to be closely related to language skills and verbal working memory.