Incidence rates of posttraumatic stress disorder (PTSD) following traumatic experiences differ between adults and children. Further, biological correlates and predictors of PTSD also seem to differ between adults and children, and between males and females. The current presentation will first describe PTSD and the incidence rates of PTSD following various types of traumatic experiences. Next, the biology of PTSD will be described, with a specific focus on abnormalities of the biological stress pathways. Special attention will be paid to abnormalities that are present soon after a traumatic experience that may serve as predictors for the development of PTSD; differences in these risk factors by gender and age will be highlighted. Finally, early secondary intervention approaches will be discussed, both psychosocial and pharmacological. Discussion will focus on how these findings could aid in and inform the design of novel studies involving cancer patients.