Eighty eight male and female subjects, pretested on Mach IV, enacted four role-plays from the Extended Interaction Test. These situations varied in social -interpersonal context, but each required the expression of negative asserti veness (i.e., to stand up for one's rights). Half of the subjects interacted with a persistent partner while the other half dealt with an easy-going one. Responses were videotaped and rated on three measures of speech content and three measures of nonverbal behavior, as well as a measure of perceived overall asserti veness. Subjects also completed a battery of self-report tests which included the Marl owe -Crowne Social Desirability Scale, the Mach V Scale, and the Conflict Resolution Inventory. The results indicated that none of the self-report measures were related to behavioral assertion, including the Conflict Resolution Inventory, a widely used test of assertion. Two of the three experimental design variables yielded significant results; although Mach was not able to predict behavioral assertion, both persistence of partner and sex of the subject were found to affect the observed levels of behavioral assertion.