A novel paradigm was developed and two studies conducted to test the contribution of six conversational skills to children's friendship formation. In study 1, 4- and 5-year-olds individually played for 30 minutes with a 2-foot-tall talking doll. The doll contained a wireless hidden receiver/speaker enabling a concealed female assistant to converse with the subject. The assistant was trained to speak in an age-appropriate manner while systematically varying the competence/incompetence of her speech with regard to the following six conversational skills found by Gottman (1983) to predict friendship formation in previously unacquainted children: communication clarity and connectedness, information exchange, establishing common-ground activities, uncovering similarities and differences, conflict resolution, and self-disclosure. Results indicated that children, especially girls, who met the skilled doll were more likely to progress toward friendship than children who met the unskilled doll. Boys were unlikely to move toward friendship when the doll spoke unskillfully. Study 2 replicated and extended these findings. Sex differences in friendship formation could not be attributed to the sex of the assistant. Differences between girls in the skilled and unskilled conditions became less pronounced with repeated play sessions. A summary of the operationalization of the six conversational processes and the content of skilled and unskilled speech is appended. (Author/RH)