The turnover of high school science teachers is an especially troubling problem in urban schools with economically disadvantaged students. Because high teacher turnover rates impede effective instruction, the persistence of teacher attrition is a serious concern. Using an online survey and interviews in a sequential mixed-methods approach, this study investigates the perceptions of high school science teachers regarding factors that contribute to their employment decisions. The study also compares first-career and second-career science teachers' perceptions of retention and attrition factors and identifies conditions that urban school leaders can establish to support the retention of their science teachers. A purposeful sample of 138 science teachers from urban area New England public high schools with 50% or more Free and Reduced Price Lunch-eligible students participated in the survey. Twelve survey respondents were subsequently interviewed. In accord with extant research, this study's results suggest that school leadership is essential to fostering teacher retention. The findings also reveal the importance of autonomy, professional community, and adequate resources to support science instruction. Although mentoring and induction programs receive low importance ratings in this study, career-changers view these programs as more important to their retention than do first-career science teachers. Second-career interviewees, in particular, voice the importance of being treated as professionals by school leaders. Future research may examine the characteristics of mentoring and induction programs that make them most responsive to the needs of first-career and second-career science teachers. Future studies may also investigate the aspects of school leadership and professional autonomy that are most effective in promoting science teacher retention. [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.]