Abstract: Post-traumatic stress disorder (PTSD) has been related to ischemic heart disease (IHD), and the primary substrate for IHD is atherosclerotic burden. We aim to estimate the association between exposure to PTSD and atherosclerotic burden in PTSD-discordant twin pairs. This is a cross-sectional examination of 212 male twins during the 2016-2019 study visit of the Vietnam Era Twin Registry. Current PTSD symptom severity was assessed with the Clinician-Administered PTSD Scale for DSM-IV. PTSD-discordant twins were defined as pairs with different values of the PTSD Symptoms Scale. We regressed the log-transformed CAC Score on the PTSD Scale adjusted for potential confounders using linear mixed models and reported exponentiated coefficients. The sample had a median age of 68 (IQR67-70) years, a 15% prevalence of PTSD (median Symptom Score of 61; IQR53-81), and a median CAC Score of 111 (IQR5-346). The median CAC Score was 69 (IQR0.40-229) in twins with higher PTSD symptoms and 89 (IQR6.6-243) in their brothers with lower PTSD symptoms. The model estimated a -0.95% difference in CAC Score per unit increment in PTSD Symptoms Score within pairs (95%CI -2.6%;+0.7%), not implying a relationship between PTSD and coronary atherosclerosis in a design that inherently controls for familial and early environmental factors.