Men who have sex with men (MSM) of color are disproportionately affected by HIV in the United States. Pre-exposure prophylaxis (PrEP) using antiretroviral medications is a newer biomedical prevention modality with established efficacy for reducing the risk of acquiring HIV. We conducted formative qualitative research to explore audience reactions and receptivity to message concepts on PrEP as part of the development of prevention messages to promote PrEP awareness among black and Latino MSM in the United States. In 2013, 48 black and 42 Latino (total study sample = 90) mixed HIV serostatus MSM from Chicago, Ft. Lauderdale, and Kansas City participated in either an individual interview or focus group discussion. Men were recruited online and at community-based organizations in each city. We elicited feedback on the comprehensibility, credibility, and relevance of two draft messages on PrEP. The messages included efficacy estimates from iPrEx, a phase III clinical trial to ascertain whether the antiretroviral medication tenofovir/emtricitabine disoproxil fumarate (commercially known as Truvada) could safely and effectively prevent HIV acquisition through sex among MSM and transgender women. With participants' consent, the interviews and focus groups were recorded and transcribed. The data were then summarized and analyzed using a qualitative descriptive approach. The majority of men were unfamiliar with PrEP. It was suggested that additional information about the medication and clinical trials establishing efficacy was needed to enhance the legitimacy and relevancy of the messages. Participants sought to form an opinion of PrEP that was grounded in their own interpretation of the efficacy data. However, confusion about nonadherence among clinical trial subjects and individual versus average risk limited comprehension of these messages. Thematic overlaps suggest that message believability was connected to participants' ability to derive meaning from the PrEP efficacy data. Despite being concerned that other MSM would interpret the messages to mean that condom use was unnecessary while taking PrEP, participants themselves primarily understood PrEP as a supplement rather than a replacement for condoms. Based on their experience with taking antiretroviral medication, HIV-positive men considered condom use a more feasible form of HIV prevention than PrEP. Participants' responses suggest that more information about PrEP and the clinical trial would support the legitimacy of PrEP and the messages as a whole. These details may enhance believability in the concept of PrEP and reinforce confidence in the validity of the efficacy result.