Exposure therapy is a well-established treatment for PTSD that requires the patient to focus on and describe the details of a traumatic experience. Nightmares that refer to or replicate traumatic experiences are prominent and distressing symptoms of PTSD and appear to exacerbate the disorder. With this apparent paradox in mind, exposure therapy and the literature on sleep and PTSD are reviewed in the context of the relationship between therapeutic exposure and exposure to trauma-related stimuli that occurs in dreams. It is concluded that nightmares that replay the trauma and disrupt sleep do not meet requirements for therapeutic exposure, whereas other dreaming may aid in the recovery from trauma.