Theologically, the Pentecostal movement is characterized by the experience of the second work of grace, following conversion, a precise moment of spiritual life within the believer's sanctification process. This is the "Baptism of the Holy Spirit," already attested in the Methodist and Holiness movements, which - in the Pentecostal tradition - manifests itself through glossolalia. The author presents some of the main aspects of Pentecostal history and identity, focusing on Italian events. The second part of the book offers an extensive and reasoned critical bibliography on Italian Pentecostalism.