Sandwiched between China, a country with high prevalence of hepatitis B surface antigen (HBsAg) and 30% of the world's HBsAg carriers, and India which has intermediate HBsAg prevalence and 10% of the world's carriers, Nepal has the lowest prevalence of hepatitis B virus (HBV) infection in Asia, with an HBsAg carrier rate of 0.9%. This treatise discusses the probable causes of this low prevalence based on published literature on the subject. The HBsAg prevalence among pregnant women in Nepal is low (0.5%) and none of those examined were HBeAg positive. The highest prevalence of HBsAg was found in the 6-15 years age group. The low prevalence of this infection in the country was due to an absence of significant vertical transmission and its predominant spread by horizontal transmission among the adolescent age group.