This study investigated posttraumatic stress disorder (PTSD) symptoms in U.S. Navy sailors assigned to guard duty in detainee operations (DETOPS, n = 444) facilities and other duties (non-DETOPS, n = 1,715) in Iraq and Afghanistan via analysis of cross-sectional, self-report surveys. The majority of DETOPS sailors reported being in serious danger of being injured or killed (61%), a frequency significantly higher (χ2 = 19.45, p < .001) than non-DETOPS sailors (49%). The assumption of measurement invariance for the PTSD Checklist was confirmed with both samples possessing the 4-factor structure identified by Simms, Watson, and Doebbelling (2002). Consistent with previous reports, the DETOPS sample was significantly higher, Wilks's λ = .98, F(5, 2146) = 10.93, p < .001, than the non-DETOPS sample when compared across 4 PTSD Checklist factors observed in the 2 samples. The percentage of sailors scoring above the threshold for probable PTSD, based on 3 scoring methods, ranged from 11.9% to 16.1%, frequencies significantly higher (p < .001) than that of the non-DETOPS sample (6.4%â€"9.6%). The results provide the first empirical evidence that DETOPS sailors in Iraq and Afghanistan were a high-risk population for developing PTSD. (PsycINFO Database Record (c) 2019 APA, all rights reserved)