Introduction: The opioid epidemic has been influenced by immense marketing campaigns produced by pharmaceutical companies. These campaigns include advertisements aimed at emergency medicine (EM) physicians, which may have influenced overprescription. This study is a part of a larger effort to systematically assess opioid ads published in major medical journals in North America. To our knowledge, this is the first study to systematically assess the volume, claims, and levels of evidence for opioid ads aimed at EM physicians. Methods: Up to two issues per year from 1996 to 2016 of ten major North American medical journals were hand-searched for opioid advertisements. Specifically, we assessed random samples of issues from five major North American emergency medicine journals, including Annals of Emergency Medicine, Emergency Medicine, Canadian Journal of Emergency Medicine, Emergency Medicine Journal, and American Journal of Emergency Medicine. Five generalist medical journals were assessed including Journal of the American Medical Association, New England Journal of Medicine, Canadian Medical Association Journal, American Family Physician, and Canadian Family Physician. The volume of advertisements, nature of the claims, and cited evidence were collected by independent reviewers. The referenced evidence was assessed using the Oxford Centre for Evidence-Based Medicine Levels of Evidence rubric. Results: Of the 269 issues across the ten journals, opioid ads compromised 95 of the 3392 pharmaceutical advertisements with 79 opioid ads available for analysis. When analysis was completed with two reviewers, inter-rater agreement was rated as 99.87 (Cohen's kappa of 0.976). 37/79 ads did not mention the addictive potential of opioids, with 60/79 not mentioning the possibility of death. The tamper potential of medications was mentioned in 27/79 ads. Positive claims included efficacy (47/79), fast-acting ability (16/79), patient preference (5/79), convenience (26/79) and reduced side effects (22/79). 26/79 cited references directly in their text. Citations were provided for a total of 19 available original studies, of which a majority (16/19) were Level 2 evidence. Upon examination of conflicts of interest, 100% (19/19) of the referenced studies were funded by a pharmaceutical company. Conclusion: A variety of claims were published in medical journals through opioid advertisements, which cite industry studies. Many ads did not mention key negative information, which may have influenced EM physician prescribing.