This ethnographic study examines the organizational structure, formation of community and ritual performance of a Catholic charismatic prayer group in the United States. Heavily influenced by the Protestant Pentecostal movement, the Catholic Charismatic Renewal (CCR) began as a grassroots movement among the Catholic laity in the late 1960s and proposed a personal connection with God through "baptism in the Holy Spirit" and reception of "charisms," spiritual gifts, such as glossolalia (speaking in tongues), healing and prophesying. Earlier studies suggested that such groups would fade out due to the inherent tension with Catholic institutions. Nevertheless, this dissertation presents the case study of a rapidly growing Catholic charismatic group at the suburbs of Boston, with a charismatic leader who is also a priest. The research methods include participant observation of all the meetings, retreats, and rituals, formal and informal interviews of the leader, his clerical associates and members, and review of the groups' publications and the leader's own radio program, during a period of twenty months from December 2001 to August 2003. I have also visited and interviewed priests and lay people of non-charismatic Catholic churches and two Protestant Pentecostal churches in the greater Boston area. Building upon Max Weber's theory of charisma, this dissertation examines how the charismatic leader maximizes his authority by integrating both personal and institutional charisma. The vertical ties the community members cultivate with the leader and the horizontal ties they establish among themselves through narratives of conversion and healing experience reinforce group cohesion and resilience. By analyzing ritual language and bodily movement, this study argues that ritual is a communication system in which the charisma of the leader and the religious experience of the followers are embodied. This study of the actual workings of a charismatic group within the hierarchical structure of the church not only advances the relationship between charisma and institution beyond the Weberian paradigm but also situates the case study of charismatic leadership within the social and historical context of American culture at large.