Background: The aim of this study was to examine the degree to which children with intellectual disability (ID) depend on manual signs during their expressive vocabulary acquisition, in relation to child and social-environmental characteristics. Method: Expressive vocabulary acquisition in speech and manual signs was monitored over a 2-year period in 23 children with ID using parent report. The children's cognitive, communicative, and vocabulary comprehension skills were measured at baseline. Speech-language pathologists' and parents' use of and attitudes towards manual signs were measured using self-report. Results: Four distinct profiles of vocabulary acquisition were evident. Those children who initially demonstrated the most significant cognitive, communicative, and comprehension delays acquired the smallest expressive vocabularies during follow-up, yet these variables were not related to the children's degree of dependence on manual signs. Conclusions: Specific cognitive, communicative, and comprehension skills relate to vocabulary acquisition. The same skills that allow for speech development seem to be fundamental to the acquisition of manual signs. (Contains 1 table and 1 figure.)