Background: Professional society conferences are integral to the medical profession. However, airline travel is a major contributor to greenhouse gas production, and the environmental impact of in-person attendance at an orthopaedic conference has yet to be described. With growing concern about the climate crisis, we sought to quantify the carbon footprint of in-person attendance to help potential attendees more consciously consider in-person attendance, inform strategies to minimize greenhouse gas emissions during travel to annual meetings, and increase awareness about and momentum for efforts in orthopaedic surgery to reduce the carbon footprint of society conferences., Questions/purposes: (1) What was the magnitude of greenhouse gas production resulting from all-in-person 2019 American Orthopaedic Foot and Ankle Society (AOFAS) annual meeting attendance in Chicago, IL, USA? (2) What was the magnitude of greenhouse gas production resulting from the all-virtual 2020 AOFAS annual meeting, and how does it compare with the 2019 AOFAS annual meeting carbon footprint? (3) To what extent could an alternative in-person meeting model with four or seven hubs decrease greenhouse gas production resulting from round-trip air travel compared with the 2019 AOFAS annual meeting?, Methods: A list of the postal codes and countries of all 1271 registered participants attending the four-day 2019 AOFAS annual meeting in Chicago, IL, USA, was obtained from AOFAS headquarters. The 2019 conference was chosen because it was the last pre-COVID meeting and thus attendance was more likely to resemble that at prepandemic in-person conferences than more recent meetings because of pandemic travel restrictions. We estimated carbon dioxide-equivalent (CO 2 e) production from round-trip air travel using a publicly available internet-based calculator (Myclimate: https://co2.myclimate.org/en/flight_calculators/new ). Emissions produced by the conference venue, car travel, and hotel stays were estimated using published Environmental Protection Agency emission factors. To estimate emissions produced by the all-virtual 2020 AOFAS annual meeting (assuming an equal number of attendees as in 2019), we used the framework published by Faber and summed estimated network data transfer emissions, personal computer and monitor emissions, and server-related emissions. Using the 2019 registrant list, we modeled four-hub and seven-hub in-person meeting alternatives to determine potential decreased round-trip air travel greenhouse gas production. Meeting hub locations were selected by visualizing the geographic distribution of the 2019 registrants and selecting reasonable meeting locations that would minimize air travel for the greatest number of attendees. Registrants were assigned to the nearest hub location. Myclimate was again used to estimate CO 2 e production for round-trip air travel for the hub meeting models., Results: The total estimated emissions of the all-in-person 2019 AOFAS annual meeting (when accounting for travel, conference space, and hotel stays) was 1565 tons CO 2 e (median 0.61 tons per attendee, range 0.02 to 7.7 tons). The total estimated emissions of the all-virtual 2020 meeting (when accounting for network data transfer emissions, personal computer and monitor emissions, and server-related emissions) was 34 tons CO 2 e (median 0.03 tons per attendee). This corresponds to a 97.8% decrease in CO 2 e emissions compared with the in-person conference. The model of a four-hub in-person meeting alternative with meetings in Chicago, Santiago, London, and Tokyo predicted an estimated 54% decrease in CO 2 e emissions from round-trip air travel. The seven-hub meeting model with meetings in Chicago; Washington, DC; Dallas; Los Angeles; Santiago; London; and Tokyo was predicted to diminish the CO 2 e emissions of round-trip air travel by an estimated 71%., Conclusion: The 2019 AOFAS annual meeting had an enormous carbon footprint and resulted in many individuals exceeding their annual allotted carbon budget (2.5 tons) according to the Paris Agreement. Hosting the meeting virtually greatly reduced the annual meeting carbon footprint, and our hub-based meeting models identified potential in-person alternatives for reducing the carbon footprint of conference attendance., Clinical Relevance: Professional societies must consider our responsibility to decarbonizing the healthcare sector by considering innovative approaches-perhaps such as our multihub proposals-to decarbonize carbon-intensive annual meetings without stalling academic progress., Competing Interests: Each author certifies that there are no funding or commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article related to the author or any immediate family members. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research ® editors and board members are on file with the publication and can be viewed on request., (Copyright © 2023 by the Association of Bone and Joint Surgeons.)