This pilot study examined, from a dynamic systems perspective, changes in maternal/child discourse behaviors across repeated readings of a storybook. Four Caucasian children (2 boys, 2 girls), ranging in age from 2 years 7 months to 2 years 10 months, were videotaped reading unfamiliar storybooks with their mothers. The videotapes were transcribed, and maternal and child behaviors were coded on several dimensions. Maternal behaviors were topic control, turn control (control of mother and child taking turns reading), and use of decontextualized language. Child discourse behaviors were topic control, turn control, lexical diversity, and decontextualized language. After 10 successive readings of the storybook, another videotape of the children reading the now familiar storybook with their mothers was made, and interactions were coded and analyzed for changes. A time frame of 3 weeks was used to control for developmental changes in child language abilities as alternative explanations for changes in child behavior. Analysis of group differences showed that mothers tended to initiate fewer extra-textual discussions with the familiar book than with the unfamiliar book, while their children concurrently initiated significantly more discussions with the familiar storybook than with the unfamiliar storybook. Three of the children assumed a more equal share of the conversation when sharing the familiar book versus the unfamiliar book. Children's lexical diversity increased significantly over the 3 weeks. In terms of individual differences, mothers varied widely on their use of decontextualized language to scaffold interactions during reading. Results were consistent with a dynamic systems perspective in which the child's competencies, the adult's scaffolding efforts, and the demands of the specific task are dynamically assembled through interactions in the context of storybook reading. (Author/KDFB)