Developed as a companion volume to "The Play's the Thing," this book defines and analyzes the concept of master player based on videotaped observations of preschool children at play. An in-depth discussion reveals the multi-faceted nature of play, individual differences in both teachers' and children's styles, and the complexity of intervention decisions made by teachers. The book is divided into 10 chapters. Chapter 1, "The Concept of the 'Master Player,'" includes information on play as representation, games and exploration, and how to support children's mastery of play. Chapter 2, "Play Watching," discusses how to observe children at play, coding child behavior, using the code, and learning through dialogue. Chapters 3 through 6 present four case studies (for example, "Tommy: Seeking Power in Play") on children's differing play attitudes. Chapter 7, "Analyzing Master Play," discusses play and cognitive development, examines the relation of play to creativity and mutuality in social interaction, dialogue, and who supports play. Chapter 8, "Becoming a Play Watcher," explores teachers as theory builders, and proposes ways of watching play and suggestions on what to look for. Chapter 9, "Becoming a Master Teacher," examines possible questions on when to intervene and proposes intervention strategies to change play. Chapter 10, "Analyzing the Integrative Behavior of Master Teachers," discusses how to code teacher integrative behavior, how to use the code, the differences among power "with," power "for," and power "on," the politics of observation, and stages of teacher development. An appendix covers teaching the art of observation. Contains about 85 references. (AA)