A study examined both the structure and the content of picture book interactions of 30 mothers with their 12-, 15-, or 18-month-old children. Interactions were videotaped in a laboratory playroom. Among the factors observed were the nature of the two partners' contributions as a function of the child's age, and the extent to which the mother gave information versus information requested by the child. The results were interpreted both in terms of L. S. Vygotsky's scaffolding construct and as revealing a general maternal orientation to elicit the maximum performance of which the child is capable. Structural aspects of the interaction were relatively constant over the age range studied: for all three age groups, the mothers controlled the interactions, taking responsibility for determining which of the pictures would be discussed. The content of the interactions varied as a function of the child's age; more active participation was demanded of older children, who were asked more questions by their mothers and who received more complex information. For all age groups, maternal questioning was related to the mother's beliefs about her child's word knowledge; she was more likely to ask the child to label a picture if she thought the child knew the label. (Several forms of maternal support for the child's performance, including feedback, are discussed.) (HTH)