Climate-sensitive open spaces within cities may have a positive effect on economic, social and environmental aspects of the urban environment. Improvement of microclimatic conditions in urban spaces can enable people to spend more time outdoors, with the potential to influence the social cohesion of a space and increase economic activity. The wider aim of this research is to develop a better understanding of the complex relationship between the microclimate and human behaviour in open public spaces in hot arid climates. Case studies are selected in two different parts of the world (Marrakech in North Africa and Phoenix, Arizona in the US) to represent a variety of users in a similar climatic context. This enables the authors to study the effects of socio-economic and cultural diversity on thermal comfort, behaviour and use of space. Field surveys include structured interviews with a standard questionnaire and observations of human activities, along with microclimatic monitoring, carried out during the summers and winters of 2008 and 2009. The analysis consists of: microclimatic influence on thermal sensation, preference and people attendance; effect of psychological adaptation on the subjective thermal evaluation of outdoor spaces; and investigation of socio-economic and socio-cultural impact on the behaviour of people in outdoor spaces.