In a recent review Evans and Cohen (1987, P. 574) identifies four general types of environmental stressors. Catastrophic events, stressful life events, daily hassles, and ambient stressors. With the exception of catastrophic events, all these areas will be covered in the present symposium. Initially, stress was studied as a response to single environmental factors. In at least one of the papers, the one on colour and physiological arousal, this approach dominates. However, already in the 1960's, stress researchers began to look at more complex human situations. This approach may be exemplified by two of the other contributions, one dealing with crowding and social support in an Indian setting, and the other with collective housing for old persons suffering from senile dementia. These contributions also exemplify the close link that exists between stress research per see and the well established fields of environmental psychology commonly referred to as personal space, crowding, and human territoriality. The importance of the concept of stress for environmental psychology emanates from the definition of stress as a generalized response to environmental factors. It is generally assumed that stress is a response to overload, resulting in a shift in bodily physiology, like blood pressure, pulse rate, and the secretion of adrenalin, noradrenalin, and cortisol. In addition there might be changes in perception, emotion, and behaviour. However, this straightforward view on the relationship between overload an stress is now being replaced by more elaborate models where cognitive or motivational factors are assumed to mediate the stress reaction (Küller 1987, p. 1251). In this context it is intriguing to take part of the hypothesis presented in one of the papers, that the breakdown of social support systems under high density living conditions may account for at least part of the deleterious effect that crowding has on mental health. The two contributions concerning colour and arousal and the activation of elderly people, however points to one of the limitations of the stress concept. Stress is commonly understood as a negative effect of too much stimulation. Therefore it often becomes necessary to point out that mild or moderate stress levels might be beneficial to the human organism. In those instances stress is instead regarded as a positive quality, and opposed to understimulation. It seems desirable to make a better distinction between the concept of stress on one hand, and the more general dimensions of activation and arousal on the other. Should we continue to regard stress as a generalized response to overload, or should stress instead be regarded as a positive force of everyday life? The organizers of lAPS 10 have asked us to look back into the future, which means we should try to compare the expectations we had twenty years ago to the present situation. I have come to the conclusion, that perhaps stress research is unique within the field of environmental psychology, in combining sound theoretical reasoning in physiology, psychology and sociology with a powerful set of methods and an eye for real world problems. Stress researcher actually seem to come to terms with a number of environmental problems (Küller 1987, P. 1267). I believe that this conclusion will become consolidated by the presentations at this symposium.