Background Illegal plasma collecting activities in mid 1990s caused a large number of human immunodeficiency virus (HIV) infections in rural areas of central-eastern China. Although most of these activities have been stopped, there were few reports on secondary transmission from infected former plasma donors to their spouses and from infected mothers to their children. This study was to determine the extent of HIV infections among young children in a rural community with a large proportion of plasma donors.Methods A survey was conducted among children aged under 7 years in a former plasma donating community in September 2000: finger blood was collected for HIV antibody testing. Another survey was repeated among children aged under 8 years and their families in the same community in April 2001: urine samples were collected for HIV testing. HIV positive children and samples of HIV negative children, whose mothers were positive based on 2001 survey, were followed up until September 2002 to investigate HIV seroconversion, disease progression and HIV strain analysis. Questionnaires were administered to collect information on childrens delivery, breast feeding, medical history and their parents commercial blood donation history and HIV status.Results Among 169 children surveyed in 2000, 10 (5.9%) were HIV positive. Of 224 children, 11 were positive in 2001. The overall prevalence rate in the two surveys was 5.0% (17/337) when counting 56 repeated children only once. Of children born to HIV positive mothers, 28.9% were infected. A seroconversion rate of 2.5 per 100 child-years was observed by following up 28 HIV negative children. No statistically significant associations were found between childrens HIV infection and their histories of blood transfusion, surgery, immunization injection or medical injections. All infections were HIV-1 subtype B strain, the average dispersion rate is 7.4%. DNA sequence analysis showed a close relationship between the seroconverted children and their infected mothers.Conclusions HIV vertical transmissions in the rural former plasma donating community was significant. Intervention measures should be taken to prevent further transmission. It was estimated that the HIV spread in this community occurred in 1994 or even earlier. Many infected people are developing AIDS now: treatment and care are urgently needed for these sick people.