Studies of negation in African American English (AAE) typically focus on its most salient exponents, ain't and negative concord. Because ain't arose during the development of auxiliary- and not-contraction in Early Modern English, an interesting question is whether constraints on ain't can be attributed to more general constraints on contraction. This article examines the constraints on not-contraction in three varieties argued to be representative of Early AAE. Although the analysis is complicated by the ever-narrowing variable context of ain't and by the competition of not-contraction with auxiliary contraction, results are largely parallel across the three varieties, pointing to a common origin. The parallels between ain't and not-contraction provide evidence that ain't is the extension of more general processes of contraction. The most consistent effect, the presence of negative concord, is argued to reflect a recurrent process of reinforcement in the history of English negation.The data on which this study is based were extracted from corpora housed in the Sociolinguistics Laboratory at the University of Ottawa. I gratefully acknowledge Professor Shana Poplack's permission to use these data. Earlier versions of this article were presented at the annual meeting of the American Dialect Society (Washington, DC, January 2001) and the third U.K. Language Variation and Change conference (York, U.K., July 2001). The analysis benefited from discussions with and comments from Greg Guy, Dennis Preston, Jennifer Smith, and Gerard Van Herk, as well as several anonymous reviewers. Special thanks go to Sali Tagliamonte and Malcah Yaeger-Dror, whose comments substantially improved the article, and to Anthony Warner for help with translating the Old English examples. Any remaining errors are my own responsibility.