Teachers, school specialists, and school administrators were asked to complete a qualitative survey on informal teacher leaders, defined as teacher leaders who have not been appointed to a designated leadership role by a school or district administrator. The survey results include respondents' perceptions of personal characteristics, knowledge and skills, and activities of informal teacher leaders, as well as the relationship of the teacher leaders with other teachers and administrators, and the impact of the informal teacher leaders on the school, teachers, and student learning.