We evaluated the main characteristics of 929 consecutive patients with chronic hepatitis B (HBV) and/or C (HCV) virus infection, who represented 79% (929/1177) of patients seen at our liver clinics between 2002-2007 Of the 929 patients,437 (47%) had chronic HBV infection, 485 (52%) chronic HCV infection and 7 (1%) chronic HBV and HCV co-infection from period A (2002-2004) to B (2005-2007), there was a trend for decrease in chronic HBV cases (50.4% vs 44.7%,P=0.10) with immigrants being responsible for 36.4% (Albanians:26.3%) of them and being more frequent in period B than A (30.6% vs 41.5%, P=0.022). In chronic hepatitis B (CHB), HBeAg-positive patients, who were more frequently immigrants than HBeAg-negative CHB patients (65.5% vs 29.5%, P<0.001), increased from period A to B (8.0% vs 17.6%, P=0.045). Intravenous drug use was reported by 41.2% of chronic HCV patients with its proportion increasing from period A to B (32.5% vs 47.4%, P=0.001). In conclusion, chronic viral hepatitis is still responsible for the majority (almost 80%0 of patients seen at Greek tertiary centers. Chronic HCV infection seems to represent the commonest cause mainly maintained by increasing numbers of intravenous drug users. There is a trend for decrease of patients with chronic HBV infection with an increasing proportion of immigrants,mostly Albanians, which results in increasing rates of HBeAg-positive CHB. Chronic hepatitis B (HBV) and C (HCV) virus infections represent two of the most common aetiologies of chronic liver diseases with their relative prevalence ranging widely from country to country.1Two to three decades ago, Greece was considered as a country of intermediate HBV endemicity with an overall prevalence of chronic HBV infection of 3-5%,2 but more recent studies demonstrated a reduction of hepatitis B surface antigen (HBsAg) prevalence to below 3%.3-6 In the nineties and after the development of reliable assays for the detection of antibodies against HCV (anti-HCV), Greece was found to be a country of relatively low HCV endemicity with an overall anti-HCV prevalence of below 2%.4,7 However, additional studies have shown that the anti-HCV prevalence is substantially higher exceeding 10% in some geographic areas8 and specific highrisk groups.9 The burden of a chronic disease on the health care system depends not only on the prevalence of this disease in the general population but on the proportion of diagnosed patients as well. The burden of a chronic disease on tertiary centers also depends on the proportion of diagnosed patients who are referred from the primary care setting. In Greece, the majority of chronic HBV and HCV patients are referred to tertiary centers for two main reasons: first, the initial confirmation of diagnosis that may require sophisticated laboratory methods or even liver biopsy cannot be made in the primary care, and second, all types of therapy for such patients are initiated at tertiary centers. In addition, many chronic HBV or HCV patients are directly seen at the outpatient clinics of tertiary centers without previous visits at primary care physicians. To date, the burden of chronic HBV and HCV infections at Greek tertiary centers, which may reflect most of the burden of these diseases in Greece has not been studied. Moreover, the effects of possible epidemiological changes associated with several factors including the arrival of great numbers of immigrants from countries of higher HBV and HCV endemicity have not been systematically examined. The aim of this retrospective study was to evaluate the burden and possible epidemiological changes of patients with the chronic HBV or HCV infection seen at our outpatient liver clinics during the last six years. In addition, changes in the use of invasive diagnostic procedures, such as liver biopsy, were also determined.