Introduction: The objective of this article is to present the rationale and baseline results for a randomized controlled pilot trial using economic incentives to reduce HIV and sexually transmitted infection (STI) risk among male sex workers (MSWs) in Mexico City. Methods: Participants (n=267) were tested and treated for STIs (chlamydia, gonorrhoea, syphilis and HIV) and viral hepatitis (hepatitis B and C), received HIV and STI prevention education and were randomized into four groups: (1) control, (2) medium conditional incentive (50/sixmonths),(3)highconditionalincentive(75/six months) and (4) unconditional incentive (50/sixmonths).Intheconditionalarms,incentiveswerecontingentupontestingfreeofnewcurableSTIs(chlamydia,gonorrhoeaandsyphilis)atfollow−upassessments.Results:Participants’meanagewas25years;825 with a 35% higher payment for condomless sex. Conclusions: The findings suggest that economic incentives are a relevant approach for HIV prevention among MSWs, given the market-based inducements for unprotected sex. This type of targeted intervention seems to be justified and should continue to be explored in the context of combination prevention efforts