Much of what is known about the acquisition of sociolinguistic competence in second language Spanish is based on studies of English-speaking learners. This body of research has demonstrated common pathways in the acquisition of multiple variable structures, as well as how second language learners come to use (or not) Spanish in linguistically and socially appropriate ways. Nevertheless, our understanding of the acquisition of sociolinguistic variation in second language Spanish is limited by the lack of systematic investigation of learners from distinct individual and social backgrounds. To that end, this dissertation explored Korean learners' acquisition and use of three variable structures in Spanish--the copula with adjectives, subject expression, and intervocalic stops. The study compared Korean-speaking learners' (N = 66), English-speaking learners' (N = 65), and native speakers' (N = 11) production of each variable structure under study in a sociolinguistic interview, a picture book description task, and a picture identification task. Additionally, an acoustic analysis of all participants' intervocalic stop production is offered. Results indicate that Korean-speaking learners' development of the copula with adjectives is associated with an increase in estar "to be" use and a decrease in omission. Subject expression development is associated with an increase in the production of null subject pronouns. Intervocalic stop development is linked to a decreased use of [f] for /p/ and of voiceless stops for /b d ?/. Inferential statistical analyses revealed various linguistic and extralinguistic factors to significantly constrain Korean-speaking learners' variable use of each linguistic structure across levels. Findings for Korean-speaking learners are directly compared to the English-speaking learners and native speakers sampled. Quantitative findings are complemented by a qualitative report of classroom observations conducted at the Korean research site. Results are discussed in relation to previous research, and contributions, limitations, and future directions are outlined and addressed. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]