Sixty undergraduate women interacted in dyads with female experimental confederates in a study of the interactive effects of social attributions and environmental controllability on interpersonal assertion. The environment was systematically varied on two dimensions of social power or control: (1) social responsiveness of the confederate, and (2) control over visual information in the interaction. As predicted, there was a significant interaction between listener responsiveness and preexisting attributions made by the speaker. Compared with their baseline voice quality during neutral messages, subjects with low self-perceived social power interacting with unresponsive confederates showed low voice assertion (content-filtered speech) during affective messages. No significant"visual access" effects were found. (Author/RL)