Collaborative virtual environments (CVEs), wherein people can virtually interact with each other via avatars, are becoming increasingly prominent. However, CVEs differ in type of avatar representation and level of behavioral realism afforded to users. The present investigation compared the effect of behavioral realism on users' nonverbal behavior, self-presence, social presence, and interpersonal attraction during a dyadic interaction. Fifty-one dyads (aged 18 to 26) embodied either a full-bodied avatar with mapped hands and inferred arm movements, an avatar consisting of only a floating head and mapped hands, or a static full-bodied avatar. Planned contrasts compared the effect of behavioral realism against no behavioral realism, and compared the effect of low versus high behavioral realism. Results show that participants who embodied the avatar with only a floating head and hands experienced greater social presence, self-presence, and interpersonal attraction than participants who embodied a full-bodied avatar with mapped hands. In contrast, there were no significant differences on these measures between participants in the two mapped-hands conditions and those who embodied a static avatar. Participants in the static-avatar condition rotated their own physical head and hands significantly less than participants in the other two conditions during the dyadic interaction. Additionally, side-to-side head movements were negatively correlated with interpersonal attraction regardless of condition. We discuss implications of the finding that behavioral realism influences nonverbal behavior and communication outcomes.