Defining the terms "Pentecostal" and "Charismatic" is a significant issue in the study of global Pentecostalism, but is not easily achieved. A clear sense of identity hinders Pentecostals from being truly ecumenical. Diversity is a primary defining issue for Pentecostal identity, although some self-definitions by Pentecostals attempt to demonstrate "distinctiveness" and create unnecessarily strained relationships with other Christians. An inclusive definition should be adopted in order to avoid both the bigotry of excluding those who do not agree with a particular understanding ofthe Scriptures and the triumphalism ofthose who boast about the growth of their own movement. Global statistics of the strength of Pentecostalism are conditioned by the authors' interpretations of their own categories. Most of the halfbillion people quoted in these statistics are not classical Pentecostals, and are predominantly Africans, Latin Americans and Asians, among whom the greatest expansion of the movement has occurred. Adopting an inclusive definition of "Pentecostal/Charismatic" will maximize the opportunities for ecumenism. Pentecostalism has contributed to nearly as many different divisions as it took the rest of the church a millennium to produce; yet Pentecostalism is both ecumenical and multicultural. If the terms are best understood as referring to those movements with an emphasis on the experience of the power ofthe Holy Spirit with accompanying manifestations of the imminent presence of God, the recognition of the unifying experiences of the Spirit has enormous potential for genuine ecumenical encounters.