Seventy-six previously unacquainted, opposite-sex pairs of undergraduate participants engaged in a 5 min videotaped interaction, then provided their mutual impressions. Research assistants coded 64 behaviours from the videotapes; these ratings were combined into behavioural factors. Participants provided self-descriptions of personality and were described by two acquaintances. Path analyses indicated that targets extraversion was associated with their behavioural involvement, which in turn was associated with partners subsequent ratings of their personality. Targets interpersonal positive affectivity was associated with their partners extraversion. Similar patterns of behavioural associations were found in relation to self-reported, partner-reported, and acquaintance-reported extraversion. These results demonstrate how extraverts may create a positive social environment through their own positivity and by creating a social press for positivity in return. Copyright © 2003 John Wiley & Sons, Ltd.