Cities by definition are a focal point of energy consumption. Their forms have a significant bearing on the balance of building and transport energy use, which are the two sectors that are directly affected by urban planning (the third being industrial). This paper establishes the relative magnitudes of building energy use in comparison to transport, and points out the interrelationships between the two in the context of the cities and of a temperate climate. The main part of the paper assesses the building energy trends and implications of urban form, with a particular reference to the effect of varying density, and presents strategic findings. It calls for continued research and development, particularly in the field of modelling the urban microclimate as a function of design, as well as comfort research with an emphasis on outdoor comfort. Urban microclimate and comfort are the themes of this journal, and this paper aims to set the scene. (C) 2003 Elsevier Science B.V. All rights reserved.