Christianity has over two billion adherents worldwide and Islam has over one and a half billion adherents, making them the two largest religions in the world, numbering, in total, over half of the world's population. It is generally assumed and taught, that because these two religions are both monotheistic, teaching that there is only one supreme God, that they basically are compatible, believing the same things about that one God. The purpose of this study is to compare and contrast the teachings of both Christianity and Islam, as found in their respective Scriptures, the Bible and the Quran and Sunna, to see exactly what they do teach and if, in fact, their teachings are compatible.