Norms are a theoretical construct that has been widely used in sociology and the social sciences more broadly. Norm theory and related empirical methods have been applied in a range of park, recreation, and tourism contexts. This chapter reviews and illustrates the resulting body of scientific and professional literature. In particular, this body of work has measured the personal and social norms of recreation visitors and other stakeholders through survey research, and illustrates the ways in which resulting data can help inform 1) standards of quality for the ecological and experiential conditions of park, recreation, and tourism areas, and 2) the associated carrying capacity of such areas. A variety of research issues are addressed, including question and response formats, norm prevalence, norm salience, evaluative dimensions of norms, crystallization of norms, norm congruence, statistical measures of norms, stability of norms, effect of existing conditions on norms, and the validity of norms.