Background. The objective of the authors' study was to characterize the clinical and pathologic differences between patients who develop posttransplant lymphoproliferative disorders (PTLD) early or late after transplantation and to assess the overall survival in these two groups. Methods. One hundred seven adult solid organ transplant patients were identified at the Mayo Clinic between Decem-ber 1970 and May 2003. Results. Forty-nine patients developed PTLD within the first year (early PTLD, 1-11.8 months) and 58 patients developed PTLD after 1 year (late PTLD, 14 months-17 years). Patients with early PTLD more commonly had the following characteristics: positive Epstein-Barr virus (EBV) in situ hybridization status (P<0.0001), CD20-positive status (P=0.002), and involvement of the grafted organ (P=0.02). Overall survival did not differ between the two groups (P=0.25). PTLD may occur in two different settings with different characteristics. Conclusions. Early PTLD is more commonly EBV in situ hybridization-positive and CD20-positive, and more commonly involves the grafted organ.