The long-term consequences of parvovirus B19 infection in transfusion recipients are not known, and thus the value of B19 screening of blood donors remains unresolved. Hemophiliacs, at risk for B19 through their chronic exposure to clotting factor concentrates, have frequent, close medical follow-up and thereby constitute an ideal group in which to study the hematologic sequelae of B19 infection. An enzyme-linked immunosorbent assay was used to detect B19 IgG and IgM and the polymerase chain reaction was used to detect B19 DNA in frozen, stored plasma samples, obtained between 1987 and 1994, from 136 subjects with hemophilia, including 71 who were human immunodeficiency virus (HIV)-positive and 65 who were HIV-negative. Then the results of the tests were compared with clinical hematological data and blood product usage data. B19 seroprevalence in the hemophilic cohort was 81.6 percent (111/136), including 74.6 percent (53/71) of HIV-positive and 89.2 percent (58/65) of HIV-negative hemophiliacs. It was not affected by age, type or severity of hemophilia, HIV status, CD4 number, or yearly blood product usage. Only 1 (0.7%) of the 136 samples was positive for B19 IgM and none was positive in polymerase chain reaction for B19 DNA. After adjusting for HIV status, there were no differences between B19-positive and B19-negative hemophiliacs in hematologic values, CD4 counts, or blood product use. Although B19 IgG seroprevalence in this hemophilic cohort is high and indicative of past B19 infection, there is no detectable B19 viral activity or any associated long-term clinical or hematologic sequelae.