This article reviews studies that have used experimental methods from psycholinguistics to address questions about the representation of sentences involving ellipsis. Accounts of the structure of ellipsis can be classified based on three choice points in a decision tree. First: does the identity constraint between antecedents and ellipsis sites apply to syntactic or semantic representations? Second: does the ellipsis site contain a phonologically null copy of the structure of the antecedent, or does it contain a pronoun or pointer that lacks internal structure? Third: if there is unpronounced structure at the ellipsis site, does that structure participate in all syntactic processes, or does it behave as if it is genuinely absent at some levels of syntactic representation? Experimental studies on ellipsis have begun to address the first two of these questions, but they are unlikely to provide insights on the third question, since the theoretical contrasts do not clearly map onto timing predictions. Some of the findings that are emerging in studies on ellipsis resemble findings from earlier studies on other syntactic dependencies involving wh-movement or anaphora. Care should be taken to avoid drawing conclusions from experiments about ellipsis that are known to be unwarranted in experiments about these other dependencies.