In this paper, we have studied how elderly people's frame of mind influences their response to experiencing nature, measured in terms of blood pressure, pulse rate, concentration and results from protocols. Two theories concerning the importance of psychological balance have been put forward earlier by Lawton and Küller, both of whom maintain that the surrounding everyday environment is one of the keys to a harmonious existence. We present findings supporting the theory that the positive experience of natural surroundings per se has a balancing and healing effect.We have found that the people most affected by their surroundings are those with the greatest psycho-physiological imbalance. When the balance tilts, the balancing effect of the green experience can restore the individual to a state of better harmony. Time spent in the outdoors is, thus, especially important for individuals who easily lose their equilibrium or find it difficult to make compensatory changes to restore harmony on their own.The research project is an intervention study in which fifteen elderly individuals living at a home for very old people participated. Their power of concentration, blood pressure and heart rate were measured before and after an hour of rest in a garden and in an indoor setting, respectively. Seven elderly people were randomly chosen to have their first series of tests in a garden, while eight elderly people had their first series of tests indoors. The results indicate that power of concentration increases for very old people after a visit in a garden outside the geriatric home in which they live, as compared to resting indoors in their favorite room.The results did not show any effects on blood pressure or heart rate. However, when we compared these results with the background variables, we found interesting correlations. Background variables included how often they took part in social activities, showed helpfulness toward other residents in group activities and tolerance/critique of other residents. After a factor analysis, the background variables formed three distinct factors, one of which showed significant correlation with blood pressure and heart rate: the factor psycho-physiological balance, with the variables "degree of tolerance," "degree of helpfulness" and "frequency of hospital visits." Elderly people with low psycho-physiological balance, that is, who had low tolerance of other residents, were not helpful in group activities and had a high frequency of hospital visits, were most affected by a stay in a garden, as could be measured in changes in heart rate and blood pressure. The results may be interpreted as showing that a garden can restore an elderly person with low psycho-physiological balance to a state of better harmony.The present study show, first, that an outdoor visit is important for recovery from stress and fatigue and, second, that the improvement is especially significant for the most susceptible. Thus, it is of particular importance that weak groups, such as elderly in great need of care, have ...