The earliest presence of Islam in Chad can be traced back to the legendary Uqba ibn Nafi, whose descendants can be found settled in the Lake Chad region to this day. By the time Arab migrants began arriving from the east in the fourteenth century in sizeable numbers, the creed was already well established. Instead of being the product of conquest or the imposition of political power, Islamization in Chad was gradual, the effect of the slow spread of Islamic civilization beyond its political frontiers.

Chadian Muslims have retained and combined pre-Islamic with Islamic rituals and beliefs. Moreover, Islam in Chad was not particularly influenced by the great mystical movements of the Islamic Middle Ages or the fundamentalist upheavals that affected the faith in the Middle East, West Africa, and Sudan. Perhaps as a result of prolonged contact with West African Muslim traders and pilgrims, most Chadian Muslims identify with the Tijaniyya order, but the brotherhood has not served as a rallying point for unified action. Similarly, the Sanusiyya, a brotherhood founded in Libya in the mid-nineteenth century, enjoyed substantial economic and political influence in the Lake Chad Basin around 1900. Despite French fears of an Islamic revival movement led by "Sanusi fanatics," Chadian adherents, limited to the Awlad Sulayman Arabs and the Toubou of eastern Tibesti, have never been numerous.

Higher Islamic education in Chad is nonexistent; thus, serious Islamic students and scholars must go abroad. Popular destinations include Khartoum and Cairo, where numerous Chadians attend Al Azhar.

Chadian observance of the five pillars of the faith differs somewhat from the orthodox tradition. For example, public and communal prayer occurs more often than the prescribed one time each week but often does not take place in a mosque. Moreover, Chadian Muslims probably make the pilgrimage less often than, for example, their Hausa counterparts in northern Nigeria. As for the Ramadan fast, the most fervent Muslims in Chad refuse to swallow their saliva during the day, a particularly stern interpretation of the injunction against eating or drinking between sunrise and sunset.

Source : http://en.wikipedia.org/wiki/Islam_in_Chad