The scientific literature discussing prevalence rates of posttraumatic stress disorder (PTSD) in the general Canadian population is relatively sparse. With the exception of a 2008 cross-sectional study in Canadians (Van Ameringen et al., 2008), the epidemiological data has come largely from the United States (Breslau et al., 1998). Despite being neighbours, Canada and the United States differ in many ways including their health care systems. As such, rates of exposure to potentially psychologically traumatic events (PPTEs; Canadian Institute for Public Safety Research and Treatment [CIPSRT], 2019) and PTSD may not be experienced to the same degree in both countries. In the current chapter, we summarize what is known about current rates of PTSD in Canadian civilians. We also examine the Canadian literature on the armed forces, as well as those in active military service, because of the high risk of trauma associated with combat exposure (Breslau, 2001). Similarly, epidemiological studies examining rates of PTSD in other populations regularly exposed to violence, disaster, and death in their occupations are presented (Breslau, 2001; Bromet, Sonnega, & Kessler, 1998; Kessler et al., 2005; Norris, 1992).