The development of a rank-size relationship in Northern Ireland is examined in relation to the all-Ireland urban system of which it formed a part until the political partition of Ireland in the 1920s. From an initial, highly irregular relationship
, which is accounted for by the existence of conflict in the entire system, the regularity of the relationship is shown to increase over time. Both aspects of the ideal rank-size relationship, linearity and a slope of 1.0, seem inapplicable as goals