Patients with critical illness who are treated in an intensive care unit (ICU) often report traumatic memories from ICU treatment, receive exogenously administered glucocorticoids for medical reasons, and have a relatively high incidence of chronic stress symptoms and posttraumatic stress disorder (PTSD) during follow-up. ICU therapy could therefore represent a useful model for investigating glucocorticoid effects on traumatic memories and PTSD development. Studies in long-term survivors of ICU treatment demonstrated a clear and vivid recall of different categories of traumatic memory such as nightmares, anxiety, respiratory distress, or pain. The incidence and intensity of PTSD symptoms increased with the number of categories of traumatic memory present. The prolonged administration of glucocorticoids (stress doses of hydrocortisone) to critically ill patients resulted in a significant reduction of PTSD symptoms measured after recovery without influencing the number of categories of traumatic memory. This protective effect of cortisol can possibly be explained by a cortisol-induced temporary impairment in traumatic memory retrieval which has previously been demonstrated in both rats and humans. Therefore, stress doses of hydrocortisone could be useful for prophylaxis and treatment of PTSD.