The genus is defined along classical lines following the works of Lloyd and Coker and Couch. Hence no review of its taxonomic features is given here. I have introduced the category of stirpes (sing. stirps) as this has been used in other mycological works, as a category for grouping related species when the characters of the groups are intergrading to the point of confusion to the taxonomist. Briefly, a stirps is a central species with its satellites. This grouping is particularly useful in Calvatia since so many of the features such as the color of the gleba, the thickness of the inner peridium, and the degree of powderiness of the mature gleba are relative, and in addition, vary some according to the age of the basidiocarp at the time it was dried. The category of stirps is without status in the International Rules of Botanical Nomenclature. The name of a stirps is the species epithet of the central species, and no authority for the name is ever used. I feel certain that this method of dividing the genus would have appealed to C. G. Lloyd were he alive today. As represented in North America the genus is divided into seven stipes and contains 32 species. The present account is not intended to be an exhaustive study of Calvatia based on the anatomy and hyphal details of the peridial layers of the basidiocarps. Rather it is an attempt to bring the classification up to date on the basis of the gross morphology of the basidiocarp and the microscopic details of the gleba. This should set the stage for a systematic study of hyphal types and detailed anatomical observations on the hyphae of the peridial walls. Such a study must necessarily be based on both fresh (immature and mature) as well as dried specimens, as the changes which take place in the maturation of the basidiocarp are certain to be of critical importance in such investigations. This means the investigator must locate mycelia of the various species and make collections of many stages in the development of the fruiting bodies. This will be a slow and tedious process, but it needs to be done in order to clarify, if possible, species as well as generic concepts in the Lycoperdales as a whole.