From 1900 through 2000, the Catholic Church has had nine popes. As the 21st century began, John Paul II was in his 22nd year as head of the church. During the century more than 600 cardinals have helped to lead the church. This biographical reference work covers all nine popes and all 641 cardinals.

The first section presents the popes in chronological order and provides date and place of birth and death, education and training for the priesthood, positions held within the church, and roles in church leadership and various conclaves. In the second section the cardinals are listed alphabetically and much the same biographical information is provided for them. (An appendix gives all the cardinals appointed by John Paul II in 2001.)