The present invention relates to the surprising discovery that certain dideoxynucleoside analogs which contain a dideoxy ribofuranosyl moiety having an L-configuration (as opposed to the naturally occurring D- configuration) exhibit unexpected activity against Hepatitis B virus (HBV). In particular, the compounds according to the present invention show potent inhibition of the replication of the virus in combination with very low toxicity to the host cells (i.e., animal or human tissue). Compounds according to the present invention exhibit primary utility as agents for inhibiting the growth or replication of HBV, HIV and other retroviruses, most preferably HBV.