The aim of this work was to obtain information on the magnitude of the problem, disease characteristics, and clinical practices relating to post-transplant lymphoproliferative disease (PTLD) in Canadian institutions. Adult and pediatric Canadian solid organ transplant groups were sent a questionnaire between July and October 1998. Analyzable data were obtained from 33 transplant groups. For the period 1988-97, 90 cases of PTLD were seen among 4283 solid organ transplant recipients. The incidence of PTLD varied from 0 to 14.6%, with the highest rates in children. Lymph nodes were the sites most frequently affected. Among the classifiable lesions, the majority were monoclonal. The lesions were of B-cell origin in 42.2% and of T-cell in 15.6%. The lesions were classified as monomorphic in 31.1%, polymorphic 18.9%, and hyperplastic in 1.1%. Tumors were reported as low grade in 26.7% and high grade in 10%. The majority of patients (71.1%) received reduced immunosuppression. Anti-viral agents were used in 52.2%. Chemotherapy was used in 27.8%, while immune globulin was used in 22.2%. Surgical resection was used in 20.0%, radiotherapy in 14.4%, and interferon-alpha therapy in 12.2%. The results showed that 48.9% of the patients had died, while 25.6% and 8.9% were regarded as having complete remission and partial remission, respectively. In conclusion, the incidence of PTLD varies widely across Canadian centres. Children are disproportionately affected and the mortality rate is high. Management practices vary significantly, and the need for information sharing was identified as one way of optimizing management.