The differences between the architecture of flats in Melbourne with flats built in Sydney during the 1920s and 1930s, suggests that these differences were manifest by factors in addition to topography. This study compares the development of architectural forms and expression in the two cities, discussing them in relation to concepts of architectural regionalism and modernism. The planning and urban redevelopment contexts result in differences in number, location, building height, lot size, site coverage, flat size, image, lifestyle and modern technology.