This chapter proposes to look in some detail at a few evocative cases, primarily from the Hellenistic and Roman periods, where associations or other groups, such as bands of worshippers, were especially concerned with purity or where they published inscribed rules of purity.1 Limited in number partly due to the vicissitudes of epigraphic preservation, partly due to the geographic and chronological specificities of this material – post-Classical Asia Minor and the Aegean – other factors may also explain their scarcity and warrant further investigation.