HIV infection rates in blood donors from the FRG were compared with the prevalence in donors from Berlin to obtain information on the HIV infections in donors of rural versus urban origin. The HIV prevalences decrease similarly in the first years of testing, although on different levels. They are lower in rural areas by a factor of 15 in the first year and of 10 thereafter. The modes of infectivity in both groups are similar although drug abuse seems to be more frequent amongst infected donors of urban areas. Ninety percent of the infected donors are either persons at risk or sexual partners of risk persons. During the observed time period there seems to be a trend from homo-/bisexuality and i.v. drug abuse to heterosexual contacts with persons at risk as the mode of infection. In conjunction with the stabile low and constant rates of infection for the last two years, these data indicate that the risk of HIV infection by blood transfusion is reduced to an acceptable minimum even in urban areas.