Despite increased availability of online promotional tools for prescription drug marketers, evidence on online prescription drug promotion is far from settled or conclusive. We highlight ways in which online prescription drug promotion is similar to conventional broadcast and print advertising and ways in which it differs. We also highlight five key areas for future research: branded drug website influence on consumer knowledge and behavior, interactive features on branded drug websites, mobile viewing of branded websites and mobile advertisements, online promotion and non-US audiences, and social media and medication decisions. A s Kim 1 notes, the emergence of online prescription drug promotion warrants research, both to inform regulation in countries that allow direct-to-consumer (DTC) promotion and to understand consumer behavior around the world. Although healthcare providers continue to be highly trusted sources of health information, consumers often first consult Internet-based sources to answer questions about health conditions or medications.2,3 At the same time, pharmaceutical companies are increasingly using online promotional tools, such as branded drug websites, online videos (eg, YouTube), and social media (eg, Facebook, Twitter, online forums, and chat rooms), to provide information about prescription drugs.4-8 Yet these online tools-as demonstrated by Kim and others [9][10][11] -often fail to present balanced information about prescription drug benefits and risks. Despite the availability of online promotional tools, however, the evidence on online prescription drug promotion is far from conclusive. Kim's study helps to address the need for new research; her overview of a decade of warning letters issued by the U.S. Food and Drug Administration (FDA) highlights some important observations. She notes that online promotion, like conventional broadcast and print advertising, harbors numerous instances of inaccurate description of drug benefits and risks. Unlike conventional broadcast advertising, however, online promotion can pose unique space constraints (such as character and space limits in Internet search engine results) that can make benefit and risk description challenging. Moreover, social media applications beg new questions about the influence of interpersonal communication online. From a regulatory perspective, we should examine additional dimensions in FDA warnings beyond Kim's current analysis. Specifically, future research should compare online DTC warnings against conventional broadcast and print ad warnings, should distinguish between notices of violation and more serious warning letters, and should compare the volume of FDA warnings against the prevalence of each DTC activity. These assessments would help to identify how online DTC violations compare to traditional DTC violations and whether the high volume of warnings for branded drug websites is because such sites are more prevalent than other online DTC activities. From a decision science perspective, we need to expand onl...