Four normal 3 1/2-year-old preschool girls who varied in degree of talkativeness were observed in a semi-naturalistic setting in order to determine the existence and nature of linguistic differences in their interactions with adults. Adult conversational partners who participated in the study were 28 college-educated females who spoke American English as their native language. Each child interacted individually with six to eight previously unfamiliar adults while at play for one half hour in a small room equipped with child-size furniture and age-appropriate toys. Each session was videorecorded. The data consisted of both adult and child talk occurring during the free play session. Each videorecorded session was transcribed until 100 adult utterances were obtained, yielding a total of 2,800 adult and accompanying child utterances. Both structural complexity and language use aspects of children's and adults' language were analyzed. Findings indicate numerous differences, both quantitative and qualitative, between the language of the two talkative and two reticent children observed. Quantitatively, the talkative children produced more of all the coded pragmatic functions and, in the discourse analysis, more adequate responses to adult- initiated comments. Qualitatively, differences were noted in structural complexity, in pragmatic functions, and in the discourse functions of the children's self-initiated speech. (Author/RH)