(Headache 2010;50:1262-1272) Objectives.— To determine the prevalence, characteristics, impact, and treatment patterns of headaches after concussion in US Army soldiers returning from a deployment to Iraq or Afghanistan. Methods.— A cross-sectional study was conducted with a cohort of soldiers undergoing postdeployment evaluation during a 5-month period at the Madigan Traumatic Brain Injury Program at Ft. Lewis, WA. All soldiers screening positive for a deployment-related concussion were given a 13-item headache questionnaire. Results.— A total of 1033 (19.6%) of 5270 returning soldiers met criteria for a deployment-related concussion. Among those with a concussion, 957 (97.8%) reported having headaches during the final 3 months of deployment. Posttraumatic headaches, defined as headaches beginning within 1 week after a concussion, were present in 361 (37%) soldiers. In total, 58% of posttraumatic headaches were classified as migraine. Posttraumatic headaches had a higher attack frequency than nontraumatic headaches, averaging 10 days per month. Chronic daily headache was present in 27% of soldiers with posttraumatic headache compared with 14% of soldiers with nontraumatic headache. Posttraumatic headaches interfered with duty performance in 37% of cases and caused more sick call visits compared with nontraumatic headache. In total, 78% of soldiers with posttraumatic headache used abortive medications, predominantly over-the-counter analgesics, and most perceived medication as effective. Conclusions.— More than 1 in 3 returning military troops who have sustained a deployment-related concussion have headaches that meet criteria for posttraumatic headache. Migraine is the predominant headache phenotype precipitated by a concussion during military deployment. Compared with headaches not directly attributable to head trauma, posttraumatic headaches are associated with a higher frequency of headache attacks and an increased prevalence of chronic daily headache.