In this study, we investigated the incidence and etiology of pericarditis and myopericarditis of military members deployed to Iraq and Kuwait from 2004 through 2008. The importance of acute pericarditis and myopericarditis in the deployed military service member has resurfaced with the reintroduction of the smallpox vaccination by the U.S. Department of Defense in 2002. There are limited epidemiologic data on acute pericarditis and myopericarditis in the general population. As a primary evacuation node for cardiology patients between 2004 and 2008, the United States Military Hospital Kuwait cardiology clinic was uniquely situated to reliably extrapolate epidemiologic data for U.S. Armed Service Members serving in the Middle East. Between these years, approximately 721,600 service members served in Kuwait and Iraq. A total of 70 cases of pericarditis and 9 cases of myopericarditis were diagnosed. This yields an estimated incidence of 7.4 and 0.95 cases per 100,000 per year for pericarditis and myopericarditis, respectively. A total of eleven patients had received the smallpox vaccine 4 to 30 days before being diagnosed with pericarditis or myopericarditis. Four of the eleven patients (36.3%) had pericarditis, with a mean duration of 28.3 days since vaccination. Seven of these eleven (63.6%) patients had myopericarditis, with a mean duration of 13.7 days since smallpox vaccination. The incidence of pericarditis and myopericarditis was lower than previously reported incidence rates in the population. In all cases of myopericarditis and pericarditis, smallpox vaccination was preferentially related to myopericarditis versus pericarditis.