The present study examined whether Snoezelen and Stimulus Preference environments have differential effects on disruptive and pro-social behaviors in adults with profound mental retardation and autism. In N = 27 adults these target behaviors were recorded for a total of 20 sessions using both multi-sensory rooms. Three comparison groups were created by diagnosis and motor respective linguistic abilities. Each client was exposed to only one multi-sensory room. Results showed that Snoezelen intervention decreased disruptive behaviors only in individuals with autism, while Stimulus Preference increased pro-social behaviors only in participants with profound mental retardation with co-occurring poor motor and linguistic abilities. Furthermore, several trend analyses of the improved behaviors were conducted throughout all sessions toward short and mid term effects of the multi-sensory room applications. These findings support both the prudence of using the Snoezelen room in individuals with developmental disabilities and the importance of using a Stimulus Preference assessment in multi-sensory environments in clients with profound mental retardation. (Contains 5 figures and 2 tables.)