The first phase of a projected research program aimed at examining children's ideas about body functioning, this study focuses on concepts of digestion, elimination of waste and assimilation of food held by children of different ages. (Subjects expressed these concepts both verbally and graphically). Possible cues to the influence of affect on these concepts are also explored. The sample consisted of 61 subjects: 20 kindergarteners, 20 third graders, and 21 seventh graders, with an equal number of boys and girls at each grade level except for the seventh grade, where there were 11 girls. Data were gathered in two interview sessions that usually took place in the same week. Measures administered in the first session included, in order, (1) an interview focused on the digestive system and its functions, (2) the Wechsler Preschool and Primary Scale of Intelligence or the Wechsler Intelligence Scale for Children, and (3) a drawing of the digestive process. Subjects were asked to draw a person at the end of the second session. Results are discussed which indicate that even the oldest children's understandings of the digestive-distributive-assimilative processes are limited. Research instruments used in the study are appended. (RH)