Within both psycholinguistic theories of parsing and formal theories of syntax, a<br/><br> distinction between arguments and adjuncts is central to some theories, while<br/><br> minimized or denied by others. Even for theories that deem the argument/<br/><br> adjunct distinction important, the exact nature of the distinction has been difficult<br/><br> to characterize. In this article, we review the psycholinguistic evidence for an<br/><br> argument/adjunct distinction, discuss how argument status can best be defined in<br/><br> the light of such evidence, and consider the implications for how grammatical<br/><br> knowledge is represented and accessed in the human mind.