This study examined the effect of changing the instructional set for written disclosure on psychological and physical health reports among traumatized college students with current posttraumatic stress symptoms. Eighty-two participants were randomly assigned to one of three writing conditions that focused on emotional expression (EE), insight and cognitive assimilation, or to a control condition. Participants assigned to the EE condition reported significant improvements in psychological and physical health 1 month following the writing sessions relative to the other two conditions. The EE participants also reported and displayed significantly greater initial psychophysiological reactivity and subsequent habituation compared with the other two conditions. These findings suggest the importance of emphasizing emotional expression during written disclosure and underscore the importance of examining how modifying the written disclosure protocol can affect outcome.