Diagnoses of 1443 patients from a population-based leukemia and allied disorders registry in Western Australia were subjected to diagnostic review, resulting in 235 deletions, 120 changes in diagnosis, and 23 undecided diagnoses. Deletions occurred mainly in lymphoma registrations, most of these being reclassified as other cancers. Among the patients whose names were deleted, 196 deaths occurred of whom 67 had leukemia or an allied disorder as the certified cause of death. Lymphoma incidence rates in Western Australia were lower than those reported from another Australian registry. Quality control of registration and special interests in diagnosis or classification of particular tumors may affect their reported incidence rates.