Emergency whole blood transfusions may increase the risk of transmitting bloodborne pathogens, including human T-lymphotropic viruses (HTLVs). U.S. military personnel with any medical encounter for HTLV infection during 2000-2013;2008 were identified from surveillance data. Using both inclusive and restrictive case definitions, the incidence of diagnoses of HTLV infection was analyzed in relation to demographic factors and prior deployment. There were 247 "possible" cases of HTLV infection identified, or 1.88 cases per 100,000 person-years (p-yrs) (95% CI 1.66, 2.13). Seventy of these met the restrictive definition, translating to a rate of 0.53 per 100,000 p-yrs (95% CI 0.42, 0.67). Under the restrictive definition, a higher rate was noted among females versus males (RR 2.37; 95% CI 1.41, 3.98), service members with a healthcare occupation versus those who are primarily trained to engage in combat (RR 2.54; 95% CI 1.06, 6.10), and service members with any deployment experience (RR 8.98; 95% CI 5.61, 14.37). These findings, and a prior military case report of transfusion-transmitted HTLV-I, suggest a need to better define the epidemiology of HTLV in U.S. military personnel to further ensure emergency transfusion safety.