& Amis: Differences in outcomes of hepatocellular carcinoma (HCC) between countries have been largely attributed to variation in the conduct of surveillance and subsequent HCC treatment eligibility. However, differences in outcomes among those detected under surveillance have not been well described. We compared characteristics and prognosis between patients with surveillance-detected HCC from the United States (US) and Japan.Patients in whom initial HCC was detected under surveillance between January 2006 and December 2015 from two centers in the US and two from Japan were included. Survival was compared between patients from the US and Japan using multivariable Cox regression analysis and propensity-score matched analysis. We performed subgroup analyses by liver disease etiology, tumor stage, and type of HCC treatment.Of 3788 HCC patients, 1797 (47.4%) were diagnosed under surveillance -715 from the US and 1082 from Japan. Patients from the US diagnosed under surveillance had worse liver dysfunction and larger tumor burden than those from Japan. In multivariate analysis, US patients with surveillance-detected HCC had significantly worse survival than those from Japan (HR 1.17, 95%CI 1.00-1.35), which was also observed in propensity-score matched analysis. However, this difference was no longer significant after adjusting for treatment type (HR 1.07, 95%CI 0.92-1.25). When stratified by treatment type, survival was comparable between the two countries except lower survival among patients who underwent resection in the US versus Japan.Prognosis of patients with surveillance-detected HCC is poorer in the US than Japan, primarily driven by differences in treatment delivery. Studies are necessary to elucidate reasons for these differences.