Posttransplant lymphoproliferative disorders (PTLD) are related to Epstein-Barr virus (EBV) and range from lymphoid hyperplasias to lymphomas. The authors report 11 transplant recipients with recurrent EBV-associated lesions. Four patients presented with EBV-positive mononucleosis-like lymphadenitis. One had recurrence of a similar lesion and the other three developed polymorphic PTLDs. Matched clonal studies in one patient showed clonal lymphoid and EB viral populations in the recurrent lesion, but not in the initial lesion. Six patients presented with polymorphic PTLDs. Five later developed histologically dissimilar tumors that resembled non-Hodgkin's lymphoma (two B-cell and one T-cell origin), Hodgkin's disease (one patient), or smooth muscle tumor (one patient). Matched clonal studies were available from one patient and showed that the primary and recurrent lesions were clonally distinct. The sixth patient had recurrence of histologically and clonally identical polymorphic PTLD. One patient presented with monomorphic PTLD and developed recurrence of a clonally identical tumor after a 6-month remission. This study shows that a few patients with EBV-associated lesions have clinical recurrence, which may be either a relapse of the original process or a new EBV-associated lesion. In some patients, the new lesion appeared to represent a more fully developed malignancy that did the antecedent lesion.