This study evaluated the effectiveness of group psychotherapy in reducing levels of shame and guilt in adult survivors of childhood sexual abuse at risk for HIV, and whether such reductions would mediate the effects of treatment on posttraumatic stress disorder (PTSD) symptoms. One hundred sixty-six women were randomized into 3 conditions: a trauma-focused group, a present-focused group, and a waitlist group. Women received 6 months of treatment and were assessed at pretreatment (T1), immediately posttreatment (T2), and 6 months posttreatment (T3). Both treatment conditions resulted in reduced shame and guilt. The treatment effect on PTSD symptoms was mediated by changes in shame, but it was not associated with changes in guilt. These findings suggest that, when treating childhood sexual abuse survivors' PTSD, it is important to address the negative self-appraisals, such as shame, that commonly accompany such symptoms.