Between 1986 and 1990, a longitudinal study called Teacher Education and Learning to Teach (TELT) was conducted by the National Center for Research on Teacher Education (NCRTE). The purposes of the study were: to investigate how formal teacher education bears on teacher learning; the impact that a variety of approaches or alternatives have on teachers' knowledge and skills; and the role of teacher education in relation to the many other influences on teacher learning. This document describes the conceptual work involved in the TELT study, its general design, and some initial findings. Major findings are grouped according to several key issues in the area of teacher education and teacher learning: (1) learning subject matter knowledge and majoring in academic subjects in college; (2) learning to accommodate diverse learners; (3) learning with the help of mentors; (4) learning in alternative certification programs; and (5) learning in preservice teacher education programs that differ in structure and orientation. The TELT study suggests that substantial changes in teaching practice are most likely to occur when teachers have extended ongoing assistance that is grounded in classroom practice, providing opportunities to try and adapt new practices in their own classrooms and enabling teachers to learn concurrently about subject matter, how diverse students learn it, and how teachers can teach it. (Author/ LL)