In the following essay I have tried to put into practice some ideas about the investigation of English Catholic communities outlined in a paper which I gave to the recusant history conference in 1965. These were much indebted to the school of sociologie religieuse inaugurated in France by M. Gabriel le Bras; I have tried to adapt its approach and methods for use in the different conditions of an English nonconfortning body. The assumptions made are that the congregation is a major object of study in the history of any Christian tradition; and that congregations, being secial entities, may best be studied by methods, including statistical methods, proper to the study of societies. In applying these assumptions to the history of English Catholicism I do not claim to be doing something different from what historians of the subject have usually done, but to be asking about single cells questions which have traditionally been aimed at the body as a whole. How big was it, and was it getting bigger or smaller? Who belonged to it, and why? Where did its members live? What relations had they with one another, outside religious belief and practice? With how much enthusiasm, with what particular emphases did they believe and practise? How did they get on with the community at large? I have sought here to answer some of these questions for four congregations in rural Northumberland between the mid-eighteenth and the mid-nineteenth century: Hesleyside alias Bellingham, Biddlestone, Thropton and Callaly. I chose this period because materials of the sort one needs were available for it; and also because it is a period of peculiar importance in the history of English Catholicism, covering the transition from its ancient to its modem phase, and providing a point of departure for enquiry in either direction. There is little significance in the communities chosen. It is incidental that the region in question should have provided most of the English support and much of the English scenery for the rebellion of 1715, or that Biddlestone should have a small niche in literary history as the original of Osbaldistone Hall in Scott’s Rob Roy. One of the characteristics of this type of investigation is that it does not much matter where one begins. Another is, however, that the value of conclusions drawn depends on. the number of cases studied. I hope to pursue some myself, but should be most happy if others were inspired to do the same. One might, in this way, reach a more intimate and comprehensive understanding of the whole English Catholic community than has so far been achieved or, I suspect, is possible for any other religious community in the country.