The inhabitants of south western Nigeria are known as the Yoruba. Their earliest contact with Islam goes back to the 14th century, but it was only in the 19th century that the faith got firmly established, as Islamic mores and intellectual culture which included medical tradition - became well entrenched. Before the advent of Islam, diagnosis of ailments, witchcraft attacks etc., was carried out through a traditional procedure which involved the use of palm kernels, cowries, the latter similar to "bone throwing" among the Zulu of South Africa. This traditional system has since lost position to divination with rosary (subha) and sand (khatt al-raml), particularly among Muslims. This development notwithstanding, elements of the indigenous medical tradition medical tradition have been incorporated into the Islamic tradition. Inam Ahmad al-Buni (d.622.H) remains a point of reference among Yorouba Muslim healers and standard works on divination with sand, for example, Ahmad al-Afandi's (fl.1290 A.H.) ilm al-raml and al-Adhami's Mizan al-adl fi masqasis ahkam al-raml (1322.A.H.) continue to be popular. Nevertheless, the native Muslim diviners have developed their own literature for this and for divination with rosary, which betrays the level of their linguistic competence as well as the degree of acculturation and hybridization of indigenous and Islamic elements in a healing custom. This paper will examine how traditional elements had been grafted on Islamic divination, and how the practitioners continue to resolve the inherent contradictions between the two phenomena in their dual role as votaries of the Islamic faith and social workers in a medical tradition with a strong religious underpinning.