This is the first of a series of papers in which we describe social relationships among mentally disabled adults who worked in four sheltered workshops. In this paper, procedures for observing and interviewing clients and for interviewing staff members were described, and data on reliability and general levels of social behavior were reported. Reliability of social behavior was significant across time and situations. Social-choice estimates were not very consistent across staff, clients, and observations. Clients spent about 40 percent of their time in informal socializing, primarily in conversation. In future papers in the series, we analyze predictors of social behavior and social choice in detail