This study examined relationship between gastrointestinal disease (GI Disease) and post-traumatic stress disorder (PTSD) in United States Military Veterans. Based upon literature and clinical practice data sources from the US Veterans Administration, GI disease and PTSD were hypothesized to be positively correlated in Veterans. The specific aims of the study were to determine the frequency with which: 1) GI Disease and PTSD are diagnosed co-morbidities; 2) a diagnosis of GI Disease accompanies a diagnosis of PTSD; and, 3) a diagnosis of PTSD accompanies a diagnosis of a GI Disease. The methodology was a retrospective, correlational design using data collect from the Department of Veteran’s Affairs Patient Database. Findings were that PTSD is bi-directionally correlated with the GI diseases of gastroesophageal reflux disease (GERD), peptic ulcer disease, functional dyspepsia, Crohn’s disease, diverticular disease, and irritable bowel syndrome (IBS), and the symptoms of constipation and nausea/vomiting within Veterans who served during wartime periods. The study also found that PTSD is not correlated with ulcerative colitis in Veterans.