At a time of heightened discourse on multilingual education in the United States, there is a need to question what is meant by the term and how its understandings may be perpetuating harmful power asymmetries. Specifically, California has declared its goal of supporting multilingual education from kindergarten through twelfth grade, yet the majority of second language offerings--high school world language programs--are not viewed as "multilingual programs" by the Department of Education. In such a context, how are world language teachers thinking about the work that they do? This dissertation examines their ideologies, conceptualized as professed beliefs, thoughts, and feelings about "a second language education" as pertaining to the language for which they were hired. In particular, it asks, (1) What are high school world language teachers' professed ideologies about "a second language education," as specific to the language for which they were hired?, and (2) What are these teachers' thoughts on multilingualism and conceptions of language, and how, if at all, might they relate to their ideologies? For data, it draws primarily on semi-structured interviews conducted with 14 Japanese, Spanish, and French teachers from eight California public high schools spanning two districts. Teachers were interviewed for at least 30 minutes, up to two times each. Interviews were audio recorded, transcribed, and analyzed through an inductive coding process at the level of utterance or strings of utterances tied together by a topical point being made. Twelve codes emerged, capturing two categories of ideologies, teachers' thoughts on multilingualism, their conceptions of language, and factors about their backgrounds and current contexts. In answer to the first research question, six ideologies were found in the data: linguistic fluency, cultural acquisition, expanding worldview, personal growth, language instruction, and student motivation. All teachers articulated two or more, showing the multidimensionality of teachers' ideologies. In answer to the second research question, teachers' thoughts on multilingualism were broadly characterized by two views: as fluency in two or more languages, and as variety in the languages. Teachers of all three languages articulated the former, but only French and Japanese teachers articulated the latter. Additionally, teachers' conceptions of language were generally found to be of five types, with possible overlap: that language is a tool for communicating, a doorway to others, a means of connection, a part of life, and abstract and ever-changing. Possible relationships between these findings are raised. Findings suggest two overall interpretations of language and its education in existence among the California high school world language teachers in this study: a proficiency interpretation and an expansiveness interpretation. Although the data were marked by the presence of both, the former--which is arguably a monolingual view of multilingualism--is far more present in state policies and existing literature. Drawing on a Foucauldian poststructuralist understanding of power, the problematic ways in which teachers' "truths" about their work reflect the "mechanisms of power" of this larger social context are discussed. Implications point toward ways in which researchers, practitioners, and policymakers might contribute to a more balanced understanding of multilingualism in world language education. [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.]