Catholics and Pentecostals in their various expressions—classical, charismatic, and Neo-Pentecostal—constitute about 75 percent of the total number of Christians today. And Pentecostals continue to grow in number. While the relations between the two traditions have often been troubled and serious theological differences remain, particularly in the area of ecclesiology, Pentecostals are beginning to show a new interest in ecumenism, and new initiatives on both sides are promising.