Simple but hitherto largely untested notions concerning the building fabric of town centres are described. An attempt is made to assemble information for 25 town centres in southern Scotland that will enable these notions to be explored empirically for two periods within this century. Difficulties encountered in compiling information in a consistent manner are discussed and the results of simple statistical tests are described. There was a tendency during both the inter-war and the post-war periods for the centres of larger towns to undergo proportionately more building replacement and facade conversion than the centres of smaller towns but the underlying processes were different in the two periods. The effect of population change on the inter-urban pattern of building replacement was marked in the post-war period but negligible in the inter-war period. The possible effects of time lags between functional changes and adjustments to the physical fabric are considered and the durability, and hence long-term significance, of the town plans and buildings of earlier periods is stressed. THE general purpose of this paper is to direct attention to a limited aspect of form-function relations that would appear to be particularly relevant to an understanding of variations between the building fabrics of towns, restricting attention to a small but focal part of the urban area-the town centre. Variations between the physiognomies of towns have attracted the attention of geographers at several times during this century and a small number of studies of varying significance have resulted (for example, Fleure, 1920; Geisler, 1924; Leighly, 1928; Solomon and Goodhand, 1965; Pillsbury, 1970; Zelinsky, I977). The chief value of these studies has been as descriptive accounts of particular cases: with rare exceptions (Davies, 1968), they were not intended to provide the basis for constructing a framework of principles of morphological development. Although urban morphology has a history going back at least to the end of the nineteenth century (Schliiter, 1899), studies of inter-urban variations in form, unlike those of function, tend to lack explicit theoretical bases. Much of the groundwork has still to be undertaken and in the mean time existing contributions lack a frame of reference by which they may be related to one another and to intra-urban studies. The embryonic nature of theory in urban morphology (Carter, 1972, P. 134) is nowhere more apparent than in the study of buildings: here even the economic constructs that figure so prominently in modern urban geography (Alonso, 1960; Christaller, 1966) have received comparatively little recognition, in spite of the acknowledged economic importance of constructional activity (Ratcliff, 1949, pp. 149, 151-3; Richardson and Aldcroft, 1968, pp. 270-5). The poor appreciation of the relevance of social constructs is less surprising in view of the lack of awareness of the social significance of the townscape (Conzen, 1966, pp. 56-6i). The lack of attention by geographers to buildings may be seen in the light of three