Five blood donors with occult persistent and one donor with an early window phase HBV infection were identified. They were negative in regular HBsAg screening and had low levels of HBV DNA that were probably not detectable by current mini-pool nucleic acid amplification testing. In four donors several mutations were found located in the HBs antigen loop. In three donors the mutations were predominantly outside the “a” determinant; one donor had a wild type HBsAg sequence. Fifty-five recipients of donations from the persistently infected donors could be tested for previous or ongoing HBV infection and of them 53% (29/55) were anti-HBc positive. Based on the prevalence of anti-HBc in Germany (7%), it was assumed that four of those recipients had already been positive before transfusion. In 22 cases, it was assumed that they acquired infection by the donations, but the infection remained asymptomatic and was resolved. In three cases transmission was proven by the time course of the acute infection and sequence identity The resulting infection was fatal and associated with immunological disorders at the time of transmission: in one case sepsis and in the other two cases immunosuppression. In a further asymptomatic case of proven transmission from the early window phase donation passively administered anti-HBs could not prevent spread of wildtype HBV but antiviral treatment lead to resolution. Surprisingly the typical acute hepatitis B was not observed in a single one of the 26 cases of assumed or proven transmission. J. Med. Virol. 79:S32–S36, 2007. © 2007 Wiley-Liss, Inc.