Investigating thermal comfort conditions in outdoor urban spaces, has thrown some light on the complexity of the issues involved, demonstrating that a quantitative approach is insufficient in describing comfort conditions outdoors. It revealed that although microclimatic parameters strongly influence thermal sensation, they cannot fully account for the wide variation between objective and subjective comfort evaluation, whereas, psychological adaptation seems to becoming increasingly important. This paper concentrates on the issue of psychological adaptation: naturalness, expectations, experience (short-/long- term), time of exposure, perceived control and environmental stimulation, and presents an attempt to try and evaluate the relative impact of each of these parameters. Understanding the interrelationship between the different parameters of psychological adaptation would be of interest in order to compare their relative significance, and to assess their design role, that is whether design considerations would influence these parameters, or vice versa, whether they could influence design decisions. An awareness of these issues would be valuable to architects, planners and urban designers, not by the way of limiting possible solutions, rather by enriching the design possibilities. (C) 2003 Elsevier Science B.V. All rights reserved.