There is a high level of suicidality among the military with PTSD. This chapter shows that those with PTSD have increased odds of both suicidal ideation and planning a suicide than those without PTSD. Hyperarousal, among the PTSD symptom clusters, is strongly associated with high-risk behaviour, suicidal thoughts and suicide attempts. Such attempts have high odds ratios with combat exposures, such as direct violence and proximity to death. These associations can be exacerbated following transition to civilian life through loss of financial and social support, as well as poor accessibility to mental health care.