Evaluation of the professional role of teacher specialists in New York City (New York) Teacher Centers was conducted through use of an innovative case study approach. Three research/evaluation questions were considered: (1) what services were being delivered? (2) what impact these services have at individual teacher, school, and district/system-wide levels? and (3) what factors accounted for these impacts and changes? Evaluation proceeded along two general lines. The first was a running documentation system used to track the delivery of teacher center services. The second included two qualitative approaches used by specialists and researchers--vignettes and pre-structured case studies. Pre-structured cases originate with a conceptual framework, specific research questions, and a set of focused instruments. Teacher Centers and teacher specialists in three different schools were the subjects of case studies. Two themes emerged from the completed case studies--the unique role of the teacher specialists and the symbolic nature of the Teacher Center. Pre-structured case studies proved to be efficient in use of time and focus. They may preclude exploring unanticipated opportunities that may arise. The qualitative approaches encouraged collaboration, shared responsibility, and improved opportunities to study complex situations. (MDE)