Cross-culture educational leadership researchers have shown in their research that national boundaries make a difference. What works in one nation may not work in another one because of different cultures in schools and across nations. This study aims to better understand the similarities and differences between American and Chinese high school principals and assistant principals' perceptions and practices of shared leadership. Six key behaviors in shared leadership were examined: visioning, building trust, sharing power and influence, developing people, and self-reflection. Mixed method research was employed in this study. An instrument, Collaborative leadership--self-assessment questionnaires, was applied to survey participants from American and Chinese high schools. Based on survey results, principals and assistant principals from two Chinese high schools and two American high schools were selected to participate in face-to-face in-depth interviews. The following selected conclusions were reached. Gender difference is small in both countries; greater leadership differentiation is found in American schools than Chinese schools; American school leaders practice shared leadership more frequently than Chinese counterparts, and the difference is mainly a function of principals' behaviors. Chinese school leaders share less in visioning; trust is built upon relationship, instruction competences and leadership experience in China, whereas in the U.S., trust is built on leadership competences; preserving harmonious relationship hinders sharing leadership in Chinese schools, while in American schools, sharing power and influence is frequently applied to obtain a broad supportive base. [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.]