Pentecostalism is one of the most dynamic forces in the church renewal movement. From fast-growing denominations such as the Assemblies of God to popular television ministries, the fruits of Pentecostalism are to be seen throughout twentieth-century American Christianity. In this controversial study, Dayton explains how Pentecostalism grew out of Methodism and the nineteenth-century American holiness movement. He finds evidence of Wesleyan teaching in the classic writings of many Pentecostal leaders. He shows how Pentecostalism is deeply rooted in the Wesleyan theological tradition, rather than being a contrived system of modern revivalist ideas. Dayton also cites evidence that Wesleyan thinkers have tried to reorient their teachings in order to put ideological "distance" between themselves and the Pentecostal movement. The study is based on little-known original sources that shed light on a number of related themes in the study of American religion and offers new perspectives on the development of 19th-century millennialism, the rise and fall of reform movements, the emergence of the healing movement, and the evolution of evangelical religion in the nineteenth century.