Besides the well-known association of Epstein-Barr virus (EBV) and lymphomas developing posttransplantation, there are only a few data concerning the prevalence of EBV antibodies (abs) in organ donors and recipients, the posttransplant development of antibody titer in the recipient population, the extent of EBV-IgM seroconversion, and the clinical and laboratory signs associated with infection. Therefore, in a retrospective analysis, we evaluated the data of 119 organ donors and 215 kidney graft recipients who received their kidney allografts between 1993 and 1995. A total of 665 sera were quantitatively tested by means of immunofluorescence assay for EBV abs against capsid (CA; IgM, IgG), early (IgG), and nuclear (IgG) antigens. Recipient sera were obtained for testing before kidney transplantation (KTx) and at post-KTx days 32, 67, and 649 (mean values). Pre-KTx all organ donors and 98.65% of the recipients wre EBV-CA-IgG positive, only in two cases was there a D+/R- (donor/recipient) combination leading to primary EBV infection. In comparison with the organ donors, in kidney graft recipients the pre-KTx IgG antibody titers (geometric mean) against EBV-CA were significantly elevated (1:428 vs 1:574; U-test). Post-KTx, EBV-CA-IgM seroconversion was observed in 29.5% (52 out of 176) of first graft recipients and in 47.8% (11 out of 23) of regrafted patients up to the last follow-up day 649. In 219 out of these 52 recipients, IgM abs again cytomegalovirus (CMV) could also be detected; the other 23 did not develop CMV-IgM abs. The most frequently associated clinical signs were fever (74%), elevated aminotransferases (57%), and deterioration of graft function (26%). In the EBV-IgM+/CMV-IgM+ group there were significantly more rejection therapies than in the EBV-IgM+/CMV-IgM- group. With respect to the severity of EBV infections, 68% were asymptomatic or mild, 27% moderate, and 4% (only 1) severe. Thus, besides the post-KTx CMV monitoring, EBV monitoring should also belong to the follow-up checks.