This report describes the trends in length of military service for active component members of the U.S. Armed Forces who were diagnosed with human immunodeficiency virus type 1 (HIV-1) infections during 1990-2013. Durations of service after service members' initial diagnoses of HIV-1 infection were compared for five different cohorts that corresponded to when diagnoses were made during the 5-year intervals beginning in 1990, 1995, 2000, and 2005, and the 4-year interval of 2010-2013. By several measures, the durations of service after initial diagnoses of HIV-1 infection increased from the earliest to the later cohorts. The findings are discussed in the context of changes in several factors during the surveillance period: the growing availability and effectiveness of treatments for HIV-1 disease; the stigmas associated with the diagnosis of HIV-1 infection and its link to homosexuality; and the changes in U.S. military policy about the inclusion of homosexuals in its ranks. Also discussed are the limitations of the estimates for the most recent cohorts and the future prospects for continued lengthening of service for those infected with HIV-1.