Women have a greater risk of developing posttraumatic stress disorder (PTSD) after exposure to trauma. Although sleep abnormalities have been implicated in the development of PTSD, gender differences in sleep soon after a traumatic event have not been investigated. This secondary analysis examined sleep characteristics using polysomnography in 13 female and 22 male trauma patients within a month of their traumatic injuries and assessed PTSD symptoms at 2-months post-injury. Results revealed more wake after sleep onset in women who developed PTSD compared to men who developed PTSD. Women with subsequent PTSD also had less total sleep time than women without subsequent PTSD. Findings suggest possible contributions of impaired sleep maintenance to the development of PTSD in women.