Journal of Medical Internet Research - International Scientific Journal for Medical Research, Information and Communication on the Internet #Preprint #PeerReviewMe: Warning: This is a unreviewed preprint. Readers are warned that the document has not been peer-reviewed by expert/patient reviewers or an academic editor, may contain misleading claims, and is likely to undergo changes before final publication, if accepted, or may have been rejected/withdrawn. Readers with interest and expertise are encouraged to sign up as peer-reviewer, if the paper is within an open peer-review period. Please cite this preprint only for review purposes or for grant applications and CVs (if you are the author). Background: Pre-exposure prophylaxis (PrEP) is an effective but under-utilized method for preventing HIV transmission in communities vulnerable to HIV. Public health campaigns aimed at increasing PrEP awareness and access have little evaluation data. Objective: We have evaluated Chicago’s PrEP campaign, PrEP4Love (P4L), a campaign that uses health-equity and sex-positivity approaches to information dissemination. Methods: PrEP4Love launched in February, 2016 and remains an active campaign today. The analysis period for this paper was from the launch date in February, 2016- May 15th, 2016. Our analysis reviews the online reach through views on social media platforms (Facebook and Instagram), “smart ads,” or ads served to individuals across a variety of web platforms based on their demographics and browsing history, and PrEP4Love website clicks. Results: 40,913,560 unique views were generated across various social media platforms. Users clicked on PrEP4Love ads 0.06 percent of the time. 32,223,987 views were received from “smart ads;” The three most clicked on ads were “STD Signs & Symptoms –More Information on STD Symptoms,” “HIV & AIDS Prevention,” and “HIV Prevention Medication.” An additional 6,970,127 views were gained through Facebook and another 1,719,446 views through Instagram. There was an average of 182 clicks per day on the PrEP4Love website. Conclusions: This is the first study investigating public responses to a health equity and sex positive social marketing campaign for PrEP. Overall, the campaign reached millions of individuals. More studies of PrEP social marketing are needed to evaluate the relationship of targeted public health campaigns on stigma and to guide future PrEP promotion strategies.