Thiswork identifies developmental stages in the acquisition of object pronouns byinstructed second language learners of Spanish. It examines learners rangingfrom beginner to advanced, where the most advanced are themselves teachers ofSpanish language courses. Experienceabroad is an important variable in the data. The book explores language production from a functionalist perspective,examining form-to-function and function-to-form mappings, and explores L2processing within the framework of the model of input processing. It providesinsights into related developments in the production of appropriate morphologyin clitic pronouns, their placement in OV contexts, and how they are processedas input. Detailed analysis revealsrelated development between the production, placement, and processing of cliticpronouns in terms of specific linguistic features, and, along with aconcept-oriented analysis of language production, we propose stages ofinterlanguage development. Finally, theextent to which classroom learning affects interlanguage development isexplored; formal instruction and experience abroad are examined, as well as thespecific instruction on object pronouns and overall exposure to instruction.