We tested the usefulness of the National Health Service Databases for investigating the incidence of lymphoid malignancies in an Italian community. We analyzed hospital discharge data, drug prescription, pathologic records and death certificates to identify the new cases of Hodgkin's disease, non Hodgkin's lymphoma, multiple myeloma, and acute and chronic lymphocytic leukemia diagnosed in the municipal population of Reggio Emilia, northern Italy, 1991 through 1996. The completeness of Hospital discharge data was very high, and several incident cases could be identified only through this source. Completeness of the pathologic registry was satisfactory for Hodgkin's disease and non-Hodgkin's lymphoma, and this source independently yielded a few incident cases of lymphoid neoplasms. Analysis of death certificates and drug prescriptions appears to be of limited value in the epidemiology of lymphoproliferative diseases.