Church documents recognize that the Catholic teacher's faith, mediated through a teacher's commitment, is one of the crucial factors that guarantees the success of the Catholic school (Congregation for Catholic Education, 1977, 1982, 2007). A number of researchers support this view with their findings (Ciriello, 1987; Tarr, 1992; Tiernan, 2000). However, until now, there has not been research that focused specifically on the relationship between Catholic teachers' faith and their commitment within the context of the Catholic high school. This dissertation study investigated (1) Catholic teachers' faith, (2) the relationships between Catholic teachers' faith and commitment, and (3) the school's three environmental characteristics associated with the relationships between Catholic teachers' faith and commitment in Catholic high schools. A national sample of 751 teachers from 39 Catholic high schools in 15 archdioceses participated in a self-administered website survey. Data were analyzed using descriptive statistics, the Pearson correlation, and a multiple hierarchical regression model. The findings of this study showed that Catholic teachers generally had a strong degree of belief, intimacy with God, action, and a living faith. And on the whole the teachers' faith degrees were stronger than typical American Catholics. There were significant relationships between the four dimensions of Catholic teachers' faith (belief, intimacy with God, action, and a living faith) and the four dimensions of their commitment (commitment to mission, the school, teaching, and students). Among the four dimensions of Catholic faith, a living faith was most influential in all the four dimensions of teacher commitment. Among the four dimensions of teacher commitment, commitment to mission was most strongly connected with all four dimensions of the faith. Lastly, the school's goals and values rooted in Catholicism, the school's community culture based on the Gospel, and the principal's spiritual leadership made significant additional contributions to Catholic teachers' commitment to the school, teaching, and students produced by their faith variables. The findings of this study strongly suggest that Catholic teachers' living faith that is placed in the center of intrinsic motivation for their school lives and activities needs to be acknowledged as a critical predictor contributing to teacher commitment. [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/en-US/products/dissertations/individuals.shtml.]