Predictors of productive and receptive language development in 39 children with intellectual disabilities (17 with Down syndrome) and their parents were identified. Children were in the prelinguistic or first stage of productive language acquisition (Brown, 1973). The Down syndrome and non-Down syndrome groups were matched on several variables, including IQ, CA, and vocabulary level. After controlling for initial language level, we attempted to identify unique early predictors of language measured 6 months later. Results indicate that Down syndrome negatively affected language development. Additionally, frequency of optimal parental responding predicted later productive language above and beyond etiology. Finally, canonical vocal communication and commenting predicted later productive language only in children without Down syndrome.