Naturalistic observations were used to monitor overt behavior in acutely ill psychiatric patients during hospitalization. Patients were observed on an individual basis in three different hospital locales: the inpatient wards, and the occupational and recreational therapy areas. The analysis was designed to determine which behaviors varied across locations as a function of the distance separating subjects and their nearest neighbors. Sex-related differences in behavior were also examined. Results showed: a) a modal distance of 1.0 to 1.5 meters separating individuals in all three locations; b) closer interpersonal distances between individuals in occupational therapy; c) significant differences in the frequency of selected behaviors in different functional areas; and d) closer interpersonal distances for females and a higher incidence of affiliative behavior by females toward males at close distances. Results are discussed in terms of environmental influences on behavioral responsiveness and sex differences in sociospatial behavior.