Background  The use of multisensory environments (MSEs) is perceived to be important for individuals with profound and multiple disabilities, although there is limited research on the efficacy of the procedures. After a search of the literature, numerous positive outcomes of MSEs were described. Our research aimed to determine whether the use of an MSE, when applied to increase the level of alertness and interaction, actually leads to this effect. Methods  A total of 15 facilities in the Netherlands and Belgium agreed to participate in the investigation. Information was gathered on the use of MSE by 177 individuals. For 62 persons, an increase of level of activity was the only stated goal. We randomly selected 20 persons out of this group for observation, using momentary time sampling as a means to relate multisensory experiences to the level of alertness and interaction. Results  The results of our study show that in general there is little evidence for an increase in activity levels as a result of MSE. There is, however, a relation between the level of activity and contextual variables. In particular, people with profound multiple disabilities have strong responses towards stimuli provided by members of staff (touching, talking to the person). Conclusions  In general, the living unit is as good a place as the MSE for promoting alertness and interactions. The influence of materials on the level of activity is limited.