The evolution of adoption institution as aspect of social structure in the society can hardly be tracedrnback to specific time and place with precision. But anthropological and historical accounts reveal thatrnadoption was commonly practiced by many ancient societies. Guddifachaa the indigenous adoptionrnpractice has been known in Oromo society. However, adoption practices in African societies in generalrnand that of Oromo people in particular were not scholarly studied and well documented. This thesisrncontribute to ethnographic works on adoption among the Oromo society.rnThe emergency of adoption practices are mainly associated with evolution of individualized family life,rnprivate property distinctive religion and social institutions such as kinship in the society. It isrnconsidered as a means by which fictive kinship is formed. In theoretical debates the development ofrnthese social institutions motivated the need to insure continuity of lineage, to get heir to property,rnsuccessor to ancestral worships and support in social life. (Goody 1990, Oâ€™ shaughnessy 1994)rnAdoption of child is also connected with biological desire of human species to replace himself orrnperpetuate his genes. In other word adoption of child provides a social progeny to infertile or childlessrncouples in the society (Goody 1969).rnPrimarily Guddifachaa, the traditional adoption practice aims at securing family line getting heir tornproperty and economic support during oldage or ill-health. Guddifachaa provides social progeny tornchildless couples in the same way adoption function in other societies. Besides these domesticrnfunctions, guddifachaa has been used at community and politico-Jural levels among Oromo society. Itrnhas been important social mechanism by which social integrations among Oromo and non-Oromornethnic groups was achieved. This thesis, illuminates this important and salient feature of adoptionrnpracticed by Oromo society and the Borana in particular. The significance of guddifachaa in providingrnlabor force in economic activities at household and community levels were highlighted. In this processrnthe traditional social mechanism of wealth distribution by means of child adoption, system of mutualrnsupport in child rearing and orphans fosterage were elaborated. Traditionally, there have been differentrninstitutions with full power and authority in ratifying, monitoring, controlling and followingrnenforcement of adoptions in Oromo society. The belief and value system of the society also providedrnmoral and ideological base for effective implementation of guddifachaa practices. The aada seerarnOromo has been customary legal base of adoption practices.rnThis thesis highlights that there has been different types of adoption institution among the Oromornpeople since ancient time. The institution has been used as an essential social strategy to resolvernproblems of foundlings or abandoned children, orphans and biologically infertile families.rnGuddifachaa practice contribute valuable institutional and value base in modern child adoptionrnfostering and placement policy formulation, planning and implementations in the country