question: Background: This study assesses the diagnostic accuracy of antigen testing compared to RT-PCR in asymptomatic collegiate athletes and describes outcomes of a surveillance testing program.Methods: Quidel Sofia-2 SARS-CoV-2 Antigen Tests were performed daily prior to sport participation for high-risk of transmission (HROT) sports from September 29, 2020-February 28, 2021. Paired RT-PCR and antigen tests were performed at least once a week. Positive antigen tests were reflexed to RT-PCR.Findings: There were 1,931 athletes in 6 HROT sports. A total of 81,175 antigen and 42,187 RT-PCR tests were performed (including 23,463 paired antigen/RT-PCR surveillance tests). There were 346 athletes (17·9%) with a positive RT-PCR test during the study period. Of the positive RT-PCRs, 83 (4·4%) occurred on paired testing days. The clinical sensitivity of antigen tests varied with the frequency of RT-PCR testing and prevalence of COVID-19. With once-a-week PCR testing, the clinical sensitivity of antigen testing was 35·7% (95% CI: 17%, 60%) and specificity 99·8% (95% CI: 99·7%, 99·9%), after adjusting for school prevalence. Daily antigen testing was similar to PCR testing 2-3 times a week in identifying infection, however, antigen testing identified infection prior to the next scheduled PCR on 89 occasions. This resulted in a 234 days where potentially infectious athletes were isolated prior to when they would have been isolated with RT-PCR testing alone. Among athletes who had RT-PCR testing 4 times a week, daily antigen testing did not increase sensitivity. Two (14%) athletic-related outbreaks occurred but 86% of infections were community-acquired.Interpretation: Screening for asymptomatic SARS-CoV-2 can be successful using different strategies. Physical mitigation is important even with frequent screening.Funding Statement: This study was funded by Quidel Corporation. Declaration of Interests: Kimberly G. Harmon declares grants from American Medical Society for Sports Medicine for Outcomes Registry for Cardiac Outcomes in Athletes;grants from Pac-12 Conference as Research Development Director, she is also the President of the American Medical Society for Sports Medicine Foundation Board. All other authors have nothing to declare. Ethics Approval Statement: The study was considered exempt by the University of Washington Institutional Review Board. Data sharing agreements for data in the Pac 12 HAP were in place for all institutions.