Developmental differences in categorization in a communication situation were investigated among 16 adult women and 16 nine-year-old children who instructed 7-year-old children in either the organization of groceries in a mock kitchen (home task) or the sorting of photographs of common objects into compartments (school task). In both tasks, the 18 items were separated into six groups and the subjects studied their locations on shelves or in compartments before instructing the 7-year-olds. Two students unaware of the purpose of the study coded each subject's references to the 18 items according to a system elaborated from Olver and Hornsby (1966). The statements were coded in terms of superordinate, functional, and nominal categories. Each of the coders rated 20 tapes, including 8 reliability tapes, which were interspersed throughout the coding phase. Results suggest that when categorization is the means to the goal of teaching children, functional categories assume great importance for adults. Category use also seems to vary according to whether communication is in an everyday context as opposed to a school or laboratory setting. (Author/RH)