Behavior categories for observations of 304 mentally disabled adults were analyzed in relation to settings (sheltered workshops and residential facility), personal characteristics (age, sex, IQ, diagnosis, and desire for affiliation) and characteristics of partners. Both settings and personal characteristics predicted individual behavior rates for the 10 most frequently observed behavior categories. As many as 14 dimensions were extracted from behavior observed in more intense dyadic relationships; these dimensions were strongly related to characteristics of the individuals in the relationships. Although more intelligent individuals exhibited higher rates of verbal behavior, they were not more verbal in their intense social relationships. Furthermore, individuals at all levels of intelligence were sensitive to the intellectual characteristics of their partners. The results suggest that the social behavior of mentally disabled people is complex and sensitive to the presence and characteristics of others; peer-group composition seems to be critical to social adaptation in communal settings for this population.