The nature of mother-child interactions when repeatedly reading the same book was examined in two dyads, one having a languageimpaired child (age 3;9), and the other a language-normal child (age 2;2) matched on mean length of utterance and expressive vocabulary. Each mother tape-recorded nine sessions reading the same picture book in her home with her son over a five month period. Each dyad displayed distinctive interaction styles, the dyad with the languageimpaired child being initially characterized by many maternal verbal obliges and many child failures to respond correctly. In later sessions, however, this child answered questions with fewer errors and become more active by contributing more statements and more verbal obliges himself. Throughout the study, the dyad with the language-normal child displayed a more equal balance of power characterized by statements and acknowledgments from both mother and child. Both children engaged in deferred imitation, introducing in later sessions labels mentiond by mothers in earlier sessions. The language-impaired child was more likely to do this if he had repeated the label when his mother first mentioned it.The effect of the linguistic environment on a child's language development is a topic of considerable interest to both researchers and clinicians. There is ample documentation that adults modify their speech to preschool children, providing a shortened and simplified speech which focuses on the 'here-and-now' (Snow 1972). This unique register, labelled motherese, has been hypothesized to facilitate language acquisition (Rondal 1985, Snow & Ferguson 1977, although there is a lack of consensus on exactly how it * We are grateful for the sustamed participation of the two mothers and their children who made this study possible