Abstract:Introduction: Millions of people have served in the Armed Forces of Ukraine (AFU) since Russia's invasion in 2014, but there is currently no information about the prevalence of posttraumatic stress disorder (PTSD) in this population. The main purpose of this study was to estimate rates of ICD-11 PTSD and Complex PTSD (CPTSD), and comorbidity with major depression, in a sample of active-duty, combat-exposed AFU military personnel. Methods: Clinical interviews were conducted with 590 soldiers recruited from military hospitals and rehabilitation centers in Ukraine. All were trauma-exposed during military operations. PTSD and CPTSD were diagnosed using the International Trauma Interview, and a current episode of major depression was diagnosed using the Mini-International Neuropsychiatric Interview. Results: Overall, 67.4% of soldiers were diagnosed with ICD-11 PTSD or CPTSD, with 45.9% being diagnosed with PTSD and 21.5% with CPTSD. Additionally, 34.4% were diagnosed with major depression, and comorbidity with PTSD (45.0%) and CPTSD (51.2%) was high. Elevated rates of PTSD were observed for current smokers and those who were currently consuming alcohol, while elevated rates of CPTSD were observed for officers (versus enlisted soldiers) and those recruited from rehabilitation facilities (vs. general hospitals). Conclusion: Although not representative of the entire AFU population, these results imply that hundreds of thousands of soldiers (and veterans) in Ukraine are likely experiencing clinically significant posttraumatic distress related to their combat experiences. Results are discussed in the context of finding scalable approaches to addressing this mental health challenge.