In the United States, an estimated 48,100 new human immunodeficiency virus (HIV) infections occurred in 2009 (1). Of these, 27% were in heterosexual men and women who did not inject drugs, and 64% were in men who have sex with men (MSM), including 3% in MSM who inject drugs. In January 2011, following publication of evidence of safety and efficacy of daily oral tenofovir disoproxil fumarate 300 mg (TDF)/emtricitabine 200 mg (FTC) (Truvada, Gilead Sciences) as antiretroviral preexposure prophylaxis (PrEP) to reduce the risk for HIV acquisition among MSM in the iPrEx trial, CDC issued interim guidance to make available information and important initial cautions on the use of PrEP in this population. Those recommendations remain valid for MSM, including MSM who also have sex with women (2). Since January 2011, data from studies of PrEP among heterosexual men and women have become available, and on July 16, 2012, the Food and Drug Administration (FDA) approved a label indication for reduction of risk for sexual acquisition of HIV infection among adults, including both heterosexuals and MSM.* This interim guidance includes consideration of the new information and addresses pregnancy and safety issues for heterosexually active adults at very high risk for sexual HIV acquisition that were not discussed in the previous interim guidance for the use of PrEP in MSM.