In five experiments, participants first read grammatical sentences of English and later rated identical, structurally similar, or novel sentences for grammatical acceptability. The experimental method was modeled after ''mere exposure'' and artificial grammar learning paradigms in which preference ratings are enhanced by prior experience with the material. Participants rated sentences as more grammatical if they had read them earlier. Increased grammaticality ratings were also observed for sentences that shared syntactic structure, but not content words, with those read earlier. A single prior exposure to a similar sentence was sufficient to induce this structural facilitation effect, although more exposures enhanced the effect. We interpret the results with respect to frequency sensitive models of parsing and to syntactic priming observed in language production, and we consider the available evidence for shared representations or mechanisms for language production and comprehension.