This paper demonstrates that the five Irish early medieval church types have markedly differential distributions. In particular, most of those with antae are in the east, while most of those without antae are in the west. It is shown that this regionalism cannot be interpreted as a deliberate strategy of material differentiation on the part of particular politico-cultural groups. A reconsideration of the chronology suggests that many of the antae-less churches are relatively late, and so the division is primarily indicative of differences in the period and rate of mortared church construction, something that is influenced by both environmental and cultural factors. It is suggested that differences in church dimensions between east and west are indicative of subtle economic differences; and a range of archaeological evidence is used to sketch other economic and cultural variations. These patterns highlight the importance of exploring regionality, even when studying relatively cohesive entities such as early medieval Ireland.