<P>This monograph investigates the nature, properties, and consequences of the grammatical constraints that yield overt marking of objects in a variety of languages. The author, working within the Minimalist Program, concentrates on the syntactic and semantic behaviors of a particular class of objects: objects morphologically marked by the dative preposition in Romance languages, especially in several Spanish dialects, with consideration of similar phenomena in other languages.The central questions addressed revolve around the syntactic derivations that have accusative and dative complements and the role played by "doubling" clitics in these derivations. The analysis, concerned primarily with Case theory, unifies syntactic phenomena by isolating the grammatical factors that yield structures with accusative and dative objects.The monograph also includes an extended discussion of some classical themes of syntactic theory in the Romance languages, including asymmetries in the wh-movement of objects with clitics, and causatives.Linguistic Inquiry Monograph 34</P>