This is a case study of one teacher's beliefs, practice, and learning during his first year of participation in a problem-centered second-grade mathematics project. The teacher in this study attempted to implement an alternative approach to teaching mathematics that differed dramatically from his former practice. This study looks at his former beliefs and practice, his teaching of mathematics during his participation in the project, and the process by which he learned and consequently changed his beliefs and practice. The teacher in this study learned and consequently changed his beliefs and practice through his actual practice. Paradigm cases often consisted of alternative interpretations of classroom incidents. (Author/MKR)