The Pāñcarātra is one of the most important Hindu traditions that worship Viṣṇu as the Supreme God. Its beginnings were probably before the Christian era and it is still extant today in certain aspects of the Śrīvai̋ṇavas' religion. This volume deals with the development and history of this tradition in the 12th/13th centuries A.D. on the basis of the Pārameśvarasaṃhitā, a text written at this period in the Raṅganāthasvāmin Temple in Śrīraṅgam (South India). Insights into the social structure of the Pāñcarātra at the time of the Pārameśvarasaṃhitā's composition, the concepts of revelation and transmission, their depiction as the tradition's source, and the basic theological doctrines of the Pāñcarātra of this period. Also discussed are the fundamental ritual changes that occurred for social and political reasons during this period, these being the main reason for the text's composition.