Background Risks of transfusion-transmitted disease are currently at a record low in the developed world. Still, available methods for blood surveillance might not be sufficient to detect transmission of diseases with unknown etiologies or with very long incubation periods. Study Design and Methods We have previously created the anonymized Scandinavian Donations and Transfusions (SCANDAT) database, containing data on blood donors, blood transfusions, and transfused patients, with complete follow-up of donors and patients for a range of health outcomes. Here we describe the re-creation of SCANDAT with updated, identifiable data. We collected computerized data on blood donations and transfusions from blood banks covering all of Sweden and Denmark. After data cleaning, two structurally identical databases were created and the entire database was linked with nationwide health outcomes registers to attain complete follow-up for up to 47 years regarding hospital care, cancer, and death. Results After removal of erroneous records, the database contained 25,523,334 donation records, 21,318,794 transfusion records, and 3,692,653 unique persons with valid identification, presently followed over 40 million person-years, with possibility for future extension. Data quality is generally high with 96% of all transfusions being traceable to their respective donation(s) and a very high (>97%) concordance with official statistics on annual number of blood donations and transfusions. Conclusions It is possible to create a binational, nationwide database with almost 50 years of follow-up of blood donors and transfused patients for a range of health outcomes. We aim to use this database for further studies of donor health, transfusion-associated risks, and transfusion-transmitted disease.