The comparison of HIV prevalence among blood donations in European countries provides an indication of the relative safety of the blood supply in different countries and over time. Data between 1990 and 2004 on annual numbers of blood donations and HIV prevalence in blood donations were collected from national correspondents in the 52 countries of the World Health Organization European Region. Data are presented for three geographic areas: West, Centre and East. Since 1990, the number of blood donations has declined by 43% in the East and by 26% in the Centre, while remaining relatively stable in the West. In 2004, the number of blood donations was more than twice as high in the West in comparison with the East and the Centre. Over the same period, HIV prevalence among blood donations increased dramatically in the East, remained stable in the Centre and declined in the West. Since 2001, HIV prevalence levels of more than 10 per 100 000 donations were reported from six countries in the East (with a high of 128/100 000 in Ukraine), whereas in the rest of Europe the reported national HIV prevalence levels were lower than 10/100 000 donations. The prevalence of HIV was much lower among donations from repeat donors than from first-time donors. In some eastern European countries public health interventions, such as deferring individuals at risk of HIV infection from donating blood and constituting a pool of regular donors, are urgently needed to assure the safety of the blood supply.