BACKGROUND: Donor-directed antibodies (DDA) can be formed in recipients after transplantation. There is not much known about their appearance in relation to the time after transplantation, nor the duration between transplantation and failure. METHODS: DDA formation was retrospectively analyzed in patients transplanted between 1992 and 2004. Thirty-two nonimmunized first transplant recipients with transplantectomy within 4 weeks (median 6 days) were analyzed. Posttransplant sera were screened for HLA class I and II by flow cytometry (FC), ELISA, and cytotoxicity. All patients except one were treated with CNI (calcineurin inhibitor)-based immunosuppression. RESULTS: Analysis was performed on the basis of FC results. In total, 16 of 32 patients became positive for DDA class I and/or II (50%). All antibodies were detected after transplantectomy. Class I and II antibodies were produced in 15 and 10 recipients, respectively. Multivariate regression analysis showed DDA positivity to be predicted by donor age (P=0.05). DDA were shown in patients who lost their graft due to immunological reasons but in a comparable percentage also in patients with nonimmunological graft loss. CONCLUSIONS: DDA after early transplantectomy appeared frequently but later than expected. In view of the growing number of marginal donors and the possible necessity of retransplantation, it is considered important to prolong the time of serum sampling and screening to at least 4 months. Immunization might escape attention when serum screening is restarted only from the time the patient is again referred to the waiting list.