In morphology, researchers have provided compelling evidence for the storage of compositional structures that could otherwise be computed by rule. In syntax, evidence of storage of fully compositional structures has been less forthcoming. We approach this question using syntactic priming, a method exploiting the tendency of individuals to repeat recently produced syntactic structures. We investigate relative clauses (RCs), which are syntactically complex but are nevertheless frequent in natural language. Across three experiments, we observe that priming of object-extracted RCs is sensitive to a) the type of noun phrase in the embedded subject position (a full NP vs. a pronoun), and b) the type of relative pronoun (who vs. that). This suggests that the representations of some types of RCs involve storage of large units that include both syntactic and lexical information. We interpret these results as supporting models of syntax that allow for complex mixtures of stored items and computation.