The efficacy of a brief prevention program (BP) aimed at arresting the development of chronic PTSD was examined with 10 recent female victims of sexual and nonsexual assault who received 4 sessions of a cognitive-behavioral program shortly after the assault. Their PTSD and depression severity was compared with that of 10 matched recent female assault victims who received repeated assessments of their trauma-related psychopathology (assessment control; AC). The BP program consisted of education about common reactions to assault and cognitive-behavioral procedures. Two months postassault, victims who received the BP program had significantly less severe PTSD symptoms than victims in the control condition; 10% of the former group met criteria for PTSD versus 70% of the latter group. Five and a half months postassault, victims in the BP group were significantly less depressed than victims in the AC group and had significantly less severe reexperiencing symptoms.