The term "scaffolding" refers to adult behaviors that support and guide children's participation in activities, including speech events, enabling the children to extend the range of what they are able to do without assistance. A study examined how scaffolding behavior in support of expository discourse differed among preschool teachers in classroom activities with the same children. Study participants included 12 preschool children who participated in activity sessions (e.g., free play, making paper flowers, or making sandwiches) with three teachers in the Psychology Department nursery of the University of Edinburgh. Classroom discourse was recorded and transcribed, and sections in which a child's expository proposition was followed by adult responses that were semantically contingent upon the child's utterance were analyzed. The adults' responses were coded using social interactionist labels and tallied in terms of the scaffolding functions provided; e.g., shaping the child's utterance or representation through feedback; reinforcing a key phrase; maintaining joint attention; linking propositions to experience; and extending the proposition to a greater number of implications. The study found less scaffolding with 5-year-olds than 3- or 4-year-olds, though the questioning function increased with age. The amount of scaffolding provided differed among the teachers, but the distribution by type of scaffolding was remarkably consistent for all adults. (AC)