It has lately become commonplace to suspect that most household and family structures in history were much the same. Under the pugnacious influence of the Cambridge Group for the History of Population and Social Structure, historians have grown wary of drawing attention to apparently abnormal household structures, and perhaps weary of reiterating the predominance in northwestern European societies of the simple or nuclear family household. Ireland, however, was not easily squeezed into the Cambridge standard model as generated for preindustrial England. Not only were Irish households before the First World War uncomfortably large, but their bulges appeared in the wrong places. Admittedly these divergences were not great; yet to students following the path of Conrad M. Arensberg and Solon T. Kimball they betokened a more fundamental divergence between the underlying structures of English and Irish families.