The adjacent utterances of three mothers and their children, aged 22.5 to 26.5 months, were recorded and analyzed. Each mother was found most frequently to express the same semantic-syntactic relation as did her child in the preceding utterance. This correspondence appeared to be independent of the parent utterance which preceded the matching pair. This pattern suggests that parent use of new linguistic structures directed to the child follows some indication in the child's language that he/she is cognitively prepared to understand them. The second major finding was that the mothers' responses co-varied with the relative accuracy and completeness of the child's utterance. Semantically, but not syntactically, inaccurate utterances were corrected more frequently than accurate utterances. Functionally incomplete utterances were more frequently followed by expansions than by questions; responses to single word utterances showed the reverse pattern. It is suggested that accelerated development in terms of mean length of utterance may be reflective of relative proportions of single and multiword utterances in the child's speech and of mothers' tendency to expand the two types of utterances to a greater or lesser extent. (JB)