ABSTRACT: INTRODUCTION:Testosterone-boosting supplements (T-Boosters) are prominently featured on Amazon.com, with numerous dedicated pages and claims that they "naturally" increase testosterone levels. AIM:To evaluate the highest rated and frequently reviewed T-Boosters on Amazon.com to facilitate patient counseling regarding marketing myths, T-Booster formulations, and evidence for efficacy and safety. METHODS:The Amazon marketplace was queried using the key words "testosterone" + "booster," with default search settings and ranking items based on relevance. The top 5 T-Boosters identified on July 22, 2018, were reviewed based on price, ratings, reviews, manufacturer details, and ingredients. Consumer reviews were categorized using core themes in the Androgen Deficiency in the Aging Male (ADAM) questionnaire as a proxy to understand T-Booster efficacy and reanalyzed after filtration of untrustworthy comments using ReviewMeta.com, a proprietary Amazon customer review analysis software. MAIN OUTCOME MEASURES:Quantitative and qualitative evaluation of T-Boosters on Amazon.com was performed. RESULTS:The top 5 T-Boosters had an average ± SD of 2,761 ± 5,112 reviews and a rating of 4.56 ± 0.25 stars. 19 unique ingredients were identified across these T-Boosters, and literature review revealed 191 studies involving the 10 most common ingredients, of which 19% involved human subjects, 53% animal models, 15% in vitro studies, and 12% case reports or review articles. Among 37 human studies, 30% observed an increase in T levels, 3% a decrease, 46% no effect, and 22% were indeterminate. Analysis of top customer reviews from the first 2 pages of reviews for each supplement revealed differences in the ADAM score before and after ReviewMeta.com filtration. After filtration, there was a 91% decrease in users reporting increased libido, a 59% decrease in reports of increased energy, a 93% decrease in reports of improved strength/endurance, a 60% decrease in reports of improved erections, an elimination of reports of improved work performance, a 67% decrease in reports of improved sleep, and an 89% decrease in reports of improved sports ability. CLINICAL IMPLICATIONS:Our study can serve as a guide for providers to counsel patients about the efficacy of popular online T-Boosters as well as the prevalence of disingenuous reviews associated with these products on online marketplaces like Amazon.com. STRENGTHS & LIMITATIONS:Strengths include the novel approach to assess consumers' perceptions and satisfaction of T-Boosters, as well as summary information that clinicians can provide patients. Limitations include selection bias, a small number of supplements analyzed, and the proprietary nature of the Amazon review analysis software. CONCLUSION:T-Boosters are easily available online. Our investigation revealed that limited human studies have evaluated T-Boosters, resulting in no definitive findings of efficacy. In the absence of additional human studies, patients should be cautioned before considering T-Boosters, given the availability of highly effective therapies approved by the Food and Drug Administration. Balasubramanian A, Thirumavalavan N, Srivatsav A, et al. Testosterone Imposters: An Analysis of Popular Online Testosterone Boosting Supplements. J Sex Med 2019;16:203-212.