This dissertation is a study of territoriality as it may appear in children's experience of the neighborhood. A review of the literature on human territoriality reveals six major dimensions: boundaries and markers, defense and control, resources and activities, social relations, psychological qualities and identity. There is also an important developmental aspect, in which territoriality may be a natural outgrowth of human learning and maturation. An examination of theoretical approaches to child development provides some important insights toward uncovering a common process underlying territoriality and development, including an ecological definition of environment, the developmental theories of Piaget and the organismic-developmentalists, the psychoanalytic views of environmental mastery and transitional phenomena, play research, and the developmental approaches to spatial cognition. In a case study in Tucson, Arizona, the territorial dimensions of boundedness, activities, control, social relations, and identity were used as a framework for study of children's perception of and behavior in their neighborhoods. A sample of 100 children in Grades 4-6 at an elementary school were interviewed using an aerial photograph, as well as asked to provide a written description of their neighborhoods and take a Locus of Control Test. A smaller subsample of 15 was used for a more detailed study involving sketch maps, diaries, neighborhood tours, subject-employed photography, the Who Am I Test, and interviews with parents. The results suggested children's neighborhoods are well-defined spatially, and are seen primarily as an activity space. The neighborhoods were distinct from outside areas in terms of the amount, variety, and type of games and other activities, with a social organization that seemed to built upon play. However, a major portion of children's social relations, as measured by the locations of best friends, was not associated with their neighborhoods. Inside their neighborhoods were found most of the children's forts, playhouses, hideouts, and special play areas, but their favorite places were about evenly divided between locations inside and outside the neighborhoods. Neighborhood place associations were somewhat linked to personal identity, but not to locus of control. Limiting factors on the extent of the children's neighborhoods were parents, streets, and mode of transportation.