AbstractThe American public has become aware that viral infections can be transmitted by blood transfusions; however, less attention has been paid to nonviral agents that are similarly transmitted. Although donors are tested routinely for serologic evidence ofTreponema palliduminfection (syphilis), there are no other bacterial infections for which donors are routinely tested, and no testing is done routinely to detect parasitic infections. Although current preventive strategies appear effective in preventing the transmission of nonviral agents by transfusion, changing population demographics, increased travel and immigration, and increased occurrence of certain asymptomatic bacterial infections in blood donors may require new policies to maintain the safety of the U.S. blood supply. This review focuses on the parasitic and bacterial infections that might pose a risk to transfusion recipients in the U.S.