Committed to improving instructional programs, more and more teachers are playing an active role in mathematics and science reform. This book was written to assist these efforts by helping current teacher leaders be more effective in this role and support the development of aspiring teacher leaders. This volume of case studies focuses on issues teacher leaders face in their interactions with other teachers, administrators, and parents such as (1) What kind of expertise do I bring to my leadership work?, (2) How do I build support for reform?, and (3) How do I develop different kinds of relationships in my role as teacher leader? These issues are elaborated on in seven different cases presenting situations that will be very familiar to anyone who has acted as a teacher leader or worked with teacher leaders. The book also contains extensive facilitation material for each case consisting of discussion questions and activities that can be used in preservice and inservice settings to promote reflection and problem solving on teacher-leadership issues. It is a mathematics or science educator's best resource for understanding the challenges of teacher leadership, acquiring the necessary skills to serve in this capacity, and implementing lasting change in classroom practice. (Contains 56 references.) (ASK)