Physiological activation is thought to be a part of the constellation of responses that accompany social anxiety, but evidence regarding the nature of such activation is mixed. In two studies, the relationship between trait social anxiety and responses during social interaction was explored using on-line cardiovascular indexes of threat. Across Studies 1 and 2, women higher in trait social anxiety exhibited cardiovascular responses consistent with greater threat during the social interaction than those lower in social anxiety. Retrospective self-reports (Studies 1 and 2), as well as partner ratings and interaction behavior (Study 2), also revealed consistent differences as a function of trait social anxiety. Study 2 added male participants, among whom a divergence emerged between results for physiological measures and other responses. These findings have implications for understanding physiological as well as psychological processes among people with social anxiety during social interaction.