New York City represents a microcosm of the changes that are shaking the very foundations of teacher education in this country. In their efforts to find teachers for hard-to-staff schools by creating multiple pathways into teaching, districts from New York City to Los Angeles are in the midst of what amounts to a national experiment in how best to recruit, prepare, and retain teachers. This article provides an overview of a research project that examines features of these different pathways into teaching in New York City schools and the impact of these features on where teachers teach, how long they remain in the classroom, and student achievement in reading and math as measured by value-added analyses. The article provides both a conceptual framework for the study and a discussion of some of the methodological challenges involved in such research, including problems of selection bias, difficulties in documenting programmatic features, and challenges of estimating teacher effects on student achievement. (Contains 1 figure and 3 notes.)