A 20-minute videotape sample was obtained of the language interactions between 20 Down syndrome children (ages 38 to 107 months) and their mothers during informal playtime. Linguistic utterances of mothers and children were coded according to the following language categories: query, declarative, imperative, performative, feedback, imitation, self-repetition, and miscellaneous. To examine the influence of children's linguistic competence on the mothers' usage of different language parameters, children were divided into two groups: those with low levels of mean length of utterance (MLU), and those with higher levels of MLU. Analysis of mother-child interactions showed that, overall, more queries and more total utterances were directed toward low MLU children, whereas imitation strategy was employed more often with high MLU children. However, mothers' MLU did not differ significantly between the two groups; in other words, regardless of the children's linguistic competence, they were exposed to similar maternal speech. Thus, mothers of low MLU children were not necessarily providing inadequate verbal stimulation or insufficient response opportunities. Several figures are included. (JW)