Previous studies using judgments of morphosyntactic errors have shown mixed evidence for a critical period for L2 acquisition (e.g., Birdsong & Molis, Journal of Memory and Language 44: 235-249, 2001, Johnson & Newport, Cognitive Psychology 21: 60-99, 1989). This study uses anomalies in the domain of information structure, the interface between syntactic form and pragmatic function, to shed light on the effect of age of arrival on L2 performance. In two experiments, high-proficiency L2 speakers of French were presented with sentence pairs containing either expected or anomalous information structure. Subjects judged each exchange as acceptable or unacceptable. A weak post-maturational effect of age on acceptability task performance was observed, along with a high degree of nativelike performance. These results are incompatible with the traditional notion of a critical period for second language acquisition in this domain of language, and also suggest that long periods of immersion in the L2 environment can lead to nativelike performance on tasks relating to information structure.