Despite being essentially hepatotropic, hepatitis B virus has frequently been detected in peripheral blood leukocytes. In most cases, viral DNA has been detected by hybridisation, though, occasionally, evidence of viral RNA and virus-specific proteins has been reported. Though definitive evidence is lacking, it appears likely that the virus is able to replicate in at least a subfraction of these cells. The possible consequences with respect to the transmission and reactivation of virus infections are discussed.