Planning and urban policies emphasise 'sustainability', but claims that 'compact cities' are more socially sustainable and acceptable have been controversial and subject to limited empirical testing. After a brief review of the concepts and debate, we set out new empirical evidence based on household surveys linked to neighbourhood physical, map-based, and sociodemographic data for five British cities. Statistical models are developed to account for systematic variations in the main social sustainability outcomes. The results are considered both in terms of the role of particular urban form and locational measures, but also in terms of the broader patterns of effects of packages of measures. Outcomes relating to residential satisfaction, stability, neighbourhood environment, and safety are all shown to be lower in higher density/ central places, but it is also shown that a good deal of this apparent effect is due to social and demographic factors. Interaction with neighbours and participation in groups is better at medium densities, controlling for other factors, while use of local services is, as expected, greater in denser, more central locations. These findings indicate that compact cities are not 'win - win' on all dimensions of sustainability but, rather, that reductions in transport emissions will have to be weighed against social criteria. In addition, urban form has different aspects, which have differing social effects, and this knowledge could inform the future design of 'smarter' urban environments. © 2009 Pion Ltd.