This work is an investigation of the orthodox concept of exorcism in Islam. The main purpose of this study is to identify the orthodox Islamic viewpoint of spirit-possession of humans and its treatment (i.e., exorcism) based upon evidence from the Qur'An, the Sunnah, views of the sahabah (companions of Prophet Muhammad [4]) and the opinions of the early Sunnite scholars. This dissertation is comprised of an introduction, four chapters, a conclusion and two appendixes. The first chapter establishes the Islamic parameters of the spiritual world of created beings. The second chapter consists of a discussion of the orthodox understanding of spirit-possession and a delineation of the prophetic methodology of exorcism. The third chapter is devoted to a study of tabulated data from interviews with a sampling of modem-day, orthodox exorcists from various parts of the Muslim world and a brief presentation of exorcism according to Roman Catholicism. The fourth chapter consists of a comparative discussion of the second and third chapters, and it includes a conclusion in which the views of modem medicine are compared to exorcist tradition. Additionally, some questions concerning exorcism in Islam and other religions are answered.