The present study was conducted to find out the perceptions of mothers from two Nigerian ethnic groups who had children with cleft lip and palate (CLP) about the aetiology of the defect. Mothers of 16 children with CLP from the Yoruba ethnic group who attended the maxillofacial clinic of the Obafemi Awolowo University teaching hospital in southern Nigeria and 20 children with CLP from the Hausa/Fulani ethnic group who attended the maxillofacial clinic of the University of Maiduguri teaching hospital in northeastern Nigeria were interviewed over an 8-month period. We used standardised interviews including questions with ethnographic components to allow us to collect information about traditional beliefs about clefts. Interviews were recorded on tape for later analysis. Thirteen of the 16 parents from the Yoruba group attributed the aetiology of CLP to supernatural forces (evil spirits and ancestral spirits), while 16 of the 20 Hausa/Fulani parents attributed it to the "will of God". Twelve of 16 Yoruba parents had consulted traditional healers for treatment before coming to the hospital. Various plants and animal products were used to treat clefts and 10 of the Yoruba parents were referred to the hospital for further treatment by the traditional healers. Cultural and religious factors seem to have an important role in the explanations, labels and treatment that followed the birth of a child with CLP in this environment. There is a need for greater collaboration and sharing of information between modern medical practitioners and traditional healers.