To systematically review the evidence on the association between knowledge of HIV-positive status or use of antiretroviral therapy (ART) and high-risk transmission behaviors, we searched Ovid MEDLINE from 2004 to February 2012 and the Cochrane Library Database through the first quarter of 2012. Four observational studies meeting inclusion criteria addressed HIV-positive status and seven addressed the use of ART and effects on behavior. Studies including both average and high-risk populations were conducted in developed countries and were rated at least fair quality. Overall, knowledge of HIV-positive status was associated with less engagement in high-risk transmission behaviors, and the use of ART was not found to increase participation in high-risk transmission behaviors by HIV-positive individuals.