Findings are presented from a study of social interactions between hearing-impaired and hearing college students living on one floor of a mainstreamed residence hall at the Rochester (New York) Institute of Technology, home of the National Technical Institute for the Deaf. Twelve ethnographic observations were completed, and interviews were conducted with 20 residents. An ecological model is offered for describing and explaining social interactions. Four individual characteristics emerged as significant in explaining the interactions: reasons for selecting a mainstream floor and perceived advantages of living on a mainstream floor; communication skill; knowledge of one another; and feelings and attitudes toward hearing-impaired/hearing people. Environmental characteristics are also considered, including the physical setting, policies and rules related to student housing, stability of the environment, and campus culture and organization. The paper concludes with a discussion of how such a model can be used to study and explain interaction between hearing-impaired and hearing people within other contexts, including family, elementary and secondary school, and work. (JDD)