AIM:To examine the epidemiology of hepatitis B virus carrier status (HBVC) and Sonographic fatty liver (SFL) in Taiwanese adults,and to evaluate their possible interaction in inducing liver damage (LD). From an epidemiological viewpoint,we analyzed previous studies which indicated that fatty liver sensitizes host immune response to HBV infection and enhances liver damage.METHODS:A cross-sectional retrospective analysis of health records including medical history,physical examination,abdominal sonogram,blood biochemistry and hepatic virological tests. We utilized the Student's f-test,chi-square,multivariate logistic regression and synergy index to assess risks for LD.RESULTS:Among a total of 5406 Taiwanese adults (mean age 46.2 years,51.5% males),the prevalence of LD,HBVC and SFL were 12.3%,15.1% and 33.4%,respectively; 5.1% of participants had SFL plus HBVC. Muifivariate logistic regression analysis demonstrated that male gender (odds ratio (OR) = 2.8,95% confidence interval (CI):2.3-3.5),overweight state (OR = 1.6,95% CI:1.3-2.0),HBVC (OR = 2.5,95% CI:2.0-3.1) and SFL (OR = 4.2,95% CI:2.2-5.3) were independently associated with LD. Synergism analysis showed that the adjusted OR for LD in adults with HBVC-alone was 3.3 (95% CI:2.4-4.6),SFL-alone,4.7 (95% CI:3.7-6.1) and combined HBVC and SFL,9.5 (95% CI:6.8-13.3); the synergy index was 1.4 (95% CI:1.001-2.0).CONCLUSION:In Taiwanese adults,SFL plus HBVC have a significant Synergistic association with LD.