This dissertation examines how critical thinking skills are addressed in university-level intensive language programs for international students in the United States. The theoretical framework for this study was built upon Vygotsky's sociocultural theory. Three research questions inquired about language instructors' ability to conceptualize critical thinking, integration of critical thinking into intensive language programs curricula and assessment tools, and obstacles in implementation of critical thinking in language instruction. Twenty-one instructors from intensive language programs for international students at six research universities in the Northeast part of the United States participated in this study. The data collection instruments were a questionnaire and follow-up interviews. A qualitative data analysis using a coding scheme revealed that the majority of the participants did not have a strong conceptualization of critical thinking and had difficulty in articulating critical thinking as a cultural construct. The analysis also revealed that the instructors from intensive language programs with re-designed curricula that included critical thinking as learning and instructional objectives reported a high success rate in preparing international students for academic challenges unlike the instructors from language programs that follow a traditional structure-oriented approach to language teaching. Some instructors from structure-oriented language programs reported that they developed their own critical thinking materials to infuse language instruction with critical thinking instruction. Other than their programs' focus on language assessment, obstacles in implementing critical thinking into language curricula listed by the instructors included a lack of textbooks encouraging critical thinking, resistance from administrators and other instructors to re-design language curricula, students' lack of motivation to learn critical thinking, and difficulty of teaching and evaluating critical thinking. With no other studies existing on teaching critical thinking in intensive language programs in universities in the U.S., this study offers pioneering evidence and implications for (a) stronger implementation of critical thinking skills in language support programs for international students planning to pursue academic degrees, (b) reconceptualization of the notion of academic literacy to include critical thinking, (c) development of critical thinking instructional materials and textbooks for language instruction, and (d) training in critical thinking instruction in teacher education programs and professional development initiatives. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]