The principal goal of this project is to develop Y-DNA profiles for descendant groups associated with the various Breifne surnames, and to determine whether any relationship exists among these descendant groups. Another goal is to determine whether or not all bearers of a given Breifne surname belong to the same Y-DNA lineage. If all the bearers of a given Breifne surname do not belong to the same Y-DNA lineage, another goal will be to determine which lineage, if any, would be the Breifne lineage. A further goal is to find wider connections for descendant groups of surnames found in Breifne but not of Breifne origin.