Two experiments using online speech processing measures with 18-to 36-month-olds extended research by Gerken & McIntosh (1993) showing that young children's comprehension is disrupted when the grammatical determiner in a noun phrase is replaced with a nonce determiner (the car vs. po car). In Expt. 1, 18-month-olds were slower and less accurate to identify familiar nouns on nonce-article than grammatical-article trials, although older children who produced determiners in their own speech showed no disruption. However, when tested on novel words in Expt. 2, even linguistically advanced 34-month-olds had greater difficulty identifying familiar as well as newly learned object names preceded by a nonce article. Children's success in "listening through" an uninformative functor-like nonce syllable before a familiar noun was related to their level of grammatical competence, but their attention to the nonce article also varied with lexical familiarity and the overall redundancy of the processing context.