Presented here are five detailed case studies of principals (four elementary level and one junior high level) undertaken to verify and modify a theoretical model of how instructional management occurs in schools. The five principals were selected from a larger group of California Bay Area principals identified by central office personnel as effective. Long open-ended interviews were used to discover principals' views of their work, and each principal was observed at work for three full work days over an eight-week period. Researchers also observed classes and talked with teachers and students. The observers particularly looked at seven components of the instructional management model: a principal's personal characteristics, district characteristics, external characteristics, principals' management behavior, school climate, instructional organization, and student outcomes. Data analysis led to modification of the conceptual framework. The observations produced three modified antecedent categories: principal characteristics, community context, and institutional context. Researchers felt the project was most successful in producing a lengthy list of principals' instructional management behavior. (JM)