This multi-decade, ongoing project, funded by volunteers and donations, utilizes DNA testing to increase what is known about McGrath lineages, from antiquity to present. We are primarily a Y-DNA project, which is the patrilineal DNA, passed only from father to son. Matching on Y-DNA follows the surname along a particular line, assuming biological sons and a culture where surname is inherited from the father. Some of our project participants do not have Y-DNA test results, though they or a close relative have a McGrath ancestor. In addition to our main focus of Y-DNA, we also look at autosomal DNA (atDNA), which is inherited from both parents. Many of our participants have atDNA results, which FTDNA refers to as "FamilyFinder". The project is designed to find common ancestors among the distinct branches of McGrath families worldwide - and any spelling of what may be this surname. With its roots in Ireland, the McGrath heritage involved a period (around 900- to 1650 AD) in which clans were the most central social construct in Ireland. In particular a Clan McGrath could be found in the Dalcassian area of Ireland (Limerick and south) and a Termon McGrath clan could be found in County Donegal around Lough Derg and the current town of Pettigo. Other families took on the McGrath surname independent of clan membership. We see the clan period as an important historical phase, but not a boundary of our project. The McGrath name is an ancient one in Ireland, early represented as the Gaelic mac Craith, but variously spelled in todayh as McGrath, McGraw, MacCrae, MacCraw, MacGrae, MacGraith, Macrae, MacReagh, Magrath, Makrayth, McCraith, McCreagh, McCreath, McGrath, McKray, Megrath, and Megraw