The large numbers of military personnel and ships and planes returning from Vietnam present the possibility of introducing a variety of infectious diseases into the United States. Thus far, only malaria has been diagnosed in significant numbers of patients, while plague presents a threat primarily through the possible importation of infected rats and fleas. Current control programs and conditions in the United States make it extremely unlikely that any of the diseases present in Vietnam will be introduced into the United States and become serious public health problems. Sporadic cases and localized outbreaks may occur, however, and will present a problem for individual medical practitioners and local public health personnel.