The vegetation of Zion National Park (ZNP) is used to illustrate the use of various indices that describe aspects of botanical diversity. The simplest method reports the average number of vascular species per 0.01 ha (0.025 acre) macroplot. The MacArthur-Wilson index of diversity is given for each plant community of occurrence in the Park. Neither the number of species per macroplot nor the MacArthur-Wilson index show much variation among the plant communities of the Park. A third index shows the proportion of a community’s major species that reach maximum regional abundance in that community. This index records large differences among communities and is indicative of the amount of genetic diversity inherent in a community. Such information will be of interest to evolutionists, plant breeders, and horticulturists. A fourth index quantifies the degree to which major species of a community are rare elsewhere in the region. This rarity index also shows large differences among the communities considered. Since rarity has unusual appeal to humans, this index identifies communities of particular interest to users and managers. Vegetational composition upon which all indices are based is reported for the 10 major communities of ZNP. Procedures for computing each index are given.