This paper describes a study that developed and tested a research measure for investigating the concerns of teachers at different stages in the adoption of educational innovations. Through a review of the literature, the staff of the Procedures for Adopting Educational Innovations project identified seven different stages of teacher concern about innovations and then developed a 35-item Stages of Concern Checklist for assessing the concerns of individual innovation users. The checklist was first verified in a reliability study involving 132 professors and classroom teachers and then administered to a stratified sample of 411 teachers involved with the adoption of team teaching. The checklist data were factor analyzed to compare teachers' primary concerns with their years of experience with team teaching. The analysis verified the utility of the stages of concern model and found that teachers' concerns progress through different stages as they gain more experience with an innovation. (JG)