Religion scholars say the fastest-growing form of Christianity is Pentecostalism, with its exuberant worship and belief in the so-called gifts of the Spirit, including speaking in tongues and divine healing. Researchers say Pentecostals and charismatics - Catholics and others who share in Pentecostal practices - make up one-quarter of the world’s Christians, with the greatest numbers in the developing world. A new study finds the fastest-growing Pentecostal churches are tackling social problems in their communities.