The influence on child language of the role of the child, and his conversational partners, was studied at the University of Washington Developmental Psychology Laboratory Preschool. Seven lessons were recorded, three child-led sessions and four adult-led sessions. The group composition varied daily but six children to be studied were included in almost every group. Language samples of three types were obtained: child in group led by adult; child in group led by child; and child as teacher. For three children, samples of all three types were obtained; for three additional children, samples of the first two types were obtained. Several measures were computed for all language samples, including rate and mean length of utterance. Utterances were also classified according to sentence type: declarative, interrogative, imperative, etc. The pattern of results is consistent: children produce more utterances, longer sentences, and ask proportionately more questions when they are teachers than when they are members of a group being taught by an adult. There is some tendency for the same changes to occur when a child is in a group taught by a child as opposed to being taught by an adult, but the magnitude of the shift is smaller. It is concluded that the results suggest that the "teaching experience" is a valuable one for preschool children. Three figures illustrate utterances per minute, mean length of utterance, and percent of questions of the six children. A bibliography is provided. (Author/DB)