One of the pressing problems listed in the first volume of the third series of the Ulster Journal of Archaeology in 1938 was the need to discover more about the character of early ecclesiastical settlements in the North of Ireland. The material remains of the early church in the north are, however, fragmentary and scattered and have been very unevenly studied. This present work was undertaken in the belief that early ecclesiastical sites deserve more concentrated study than they have received in the past. The authors initial was to bring together the scattered notices of early sites and material, to visit the sites, record the material and look at the evidence as a whole. The search for material, however, led on to the written sources and the place-name evidence, and so the work has grown from a search for material to an exploration of the interrelationshAs between the different sources. The study is in three parts. The introductory section explores the various approaches and the sources, including a discussion of procedure. Section II pursues the themes which emerge from the introduction. The basis for all this discussion is the material presented in section III, the gazetteer and inventory, which includes 266 sites and is accompanied by illustrations.