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.IN STUDIES OF THE WRITTEN disclosure procedure developed by Pennebaker and colleagues (see Pennebaker, 1997, for a review), researchers have typically examined the physical and psychological health effects associated with written disclosure by comparing participants who are asked to write about the most traumatic or stressful experience of their lives with as much emotion as possible with a group of participants who are asked to write about an experience with no emotion. Although some studies have suggested that written disclosure is associated with improvements in physical and psychological health, findings from other studies have suggested that written disclosure may not produce significant health changes (see Sloan & Marx, 2004b, for a review). These equivocal outcomes are not surprising given that a number of investigators have unsystematically altered various aspects of the procedure, such as the number of writing sessions used (Greenberg, Wortman, & Stone, 1996;Lepore, 1997, Stroebe, Stroebe, Schut, Zech, & van den Bout, 2002, the duration of the writing sessions (Greenberg et al., 1996;Schoutrop, Lange, Hanewald, Duurland, & Bermond, 1997;Stroebe et al., 2002), and the length of time between writing sessions (Esterling, Antoni, Fletcher, Marguiles, & Schneiderman, 1994;Schoutrop et al., 1997;Stanton et al., 2002). In general, investigators have not provided a rationale for such methodological alterations, nor do they include appropriate comparison groups to examine the effect of such alterations. Making findings even more difficult to interpret is the fact that some investigators have altered multiple aspects of the procedure within the same study (e.g., Batten, Follette, Hall, & Palm, 2002;Gidron, Peri, Connonlly, & Shalev, 1996). That is, some studies have altered the instructional set, the duration of the writing sessions, and the number of writing sessions within the same study. Such alterations make it difficult to discern what might account for the null (Batten et al., 2002;Kloss & Lisman, 2002; Stroebe © 2007 Association for Behavio...