This collective volume offers an up-to-date and comprehensive state-of-the-art presentation of the research that has been done in the syntactic variation of Spanish dialects, taking into account both European and American varieties. In so doing, this book seeks to set the boundary conditions for subsequent investigations on the different manifestations of Spanish syntax and its geographic contours, a very rich (though largely neglected) area of inquiry. Such investigations should ideally lead us not only to pin down the short-range microparameters of Spanish but also to explore its similarities with other languages (closely related or not) and, ultimately, to understand the variation margins that the faculty of language offers. The volume is divided into two parts, each of them dealing with varieties of Europe and America. Empirically, the different chapters cover a wide set of syntactic phenomena and constructions, such as agreement, clitics, doubling, expletives, word order, differential object marking, pro-drop, and more. All in all, this book represents not only an important contribution in the study of Spanish syntax, but also the beginning of a new wave of formal studies of dialectal syntax.