The purpose of this dissertation study was to explore African-American women's perceptions of undergraduate STEM classroom experiences, and the ways in which those experiences have supported or hindered their persistence in physics majors. The major research question guiding this study was: How do African-American women perceive the climate and interactions with peers and faculty in undergraduate STEM classrooms? Using qualitative methods and a multiple case study design, a sample of 11 women were interviewed. This study was also informed by data from 31 African-American women who participated in focus group interviews at annual meetings of the National Society of Black and Hispanic Physicists. Findings indicated that the women excelled in small courses with faculty who took a personal interest in their success. They also perceived that there was a pervasive culture in physics and other STEM departments that often conflicted with their own worldviews. Findings also indicated that the women's perceptions of classroom experiences varied widely depending on professors' behaviors, institution types, and the level of courses. It is anticipated that through a better understanding of their perceptions of STEM learning environments and factors in their persistence, STEM faculty and departments can better retain and support this population of students.