There have been no previous reports of the prevalence of hepatatis B virus (HBV) and hepatitis C virus (HCV) infections in Lao PDR. From 2003 to 2005, 13,897 first-time blood donors were screened for the presence of hepatitis B surface antigen (HBsAg) and hepatitis C virus antibody (anti-HCV). The seroprevalence of HBsAg positive blood donors was 8.7%. The prevalence among males (9.7%) was higher than in females (6.2%). The prevalence of anti-HCV positive blood donors was 1.1%, with no significant differences between males (1.1%) and females (1.0%). Annual positive rates for HBsAg and anti-HCV during the years 2003 to 2005 did not differ significantly. Lao PDR has a high endemicity of HBV carriers (8.7%). Dual infection with HBV and HCV was 0.12%. For preventing HBV infection, the country introduced DPT-Hepatitis B vaccines into the National Immunization Program in 2001. The large reservoir of HBV and HCV infections will cause an enormous burden of patients with cirrhosis and hepatocellular carcinoma in the future.