Purpose: This study examined sentence comprehension in children with specific language impairment (SLI) in a manner designed to separate the contribution of cognitive capacity from the effects of syntactic structure. Method: Nineteen children with SLI, 19 typically developing children matched for age (TD-A), and 19 younger typically developing children (TD-Y) matched according to sentence comprehension test scores responded to sentence comprehension items that varied in either length or their demands on cognitive capacity, based on the nature of the foils competing with the target picture. Results: The TD-A children were accurate across all item types. The SLI and TD-Y groups were less accurate than the TD-A group on items with greater length and, especially, on items with the greatest demands on cognitive capacity. The types of errors were consistent with failure to retain details of the sentence apart from syntactic structure. Conclusions: The difficulty in the more demanding conditions seemed attributable to interference. Specifically, the children with SLI and the TD-Y children appeared to have difficulty retaining details of the target sentence when the information reflected in the foils closely resembled the information in the target sentence. (Contains 4 tables and 2 figures.)