"The results of a research project in 33 units of 15 nursing homes in the region of Mechelen in Flanders, Belgium show that environmental variables such as the services provided, the prosthetic aids available and the social climate ill the home have a significant influence on the functioning and well_being of persons with dementia. Moreover, the environmental features have a differential impact on severely (GDS-score of 6) and mildly demented (GDS-score between 1 and 4) elderly. The impact of the environment increases as the abilities of the person diminish, which confirms Powell Lawton's "environmental docility hypothesis". We would like to dwell on two major implications of this conclusion. Firstly, this has serious implications for the design of the unit. It could imply that the design of the unit should differ according to the degree of dementia the residents suffer from. Secondly, the findings of our research can contribute to the ongoing discussions on whether units should be organised homogeneously with only dementing residents or heterogeneously with dementing as well as non-dementing residents."